Despite the meaning of the Greek word underlying it, aphantasia does not mean that you can't imagine. It means you can't create mental images.

As an aphantasic, I can imagine just fine. If you consult the Wikipedia page on the subject, you'll find a number of famous authors listed.

You may be interested in this essay by Blake Ross, cofounder of Firefox and ex-director of product at Facebook, on discovering he had aphantasia, an insight that explained a million little things about his own personal experiences that seemed amiss relative to others. Quoting some passages (attention conservation notice -- there's ~1,000 words below):

How do you write fiction if you can’t visualize scenes?

I “imagine” scripts conceptually as described earlier. It’s easier to write for characters that have already been realized on the screen, especially when so many of them share my dry, sarcastic personality. If you reread the Silicon Valley script, you’ll find it’s heavy on ideas (what if a lawyer had a clock that counted money not time? what if Erlich compiled interview questions while stoned?) and light on descriptive language. Same with the Theranos parody.

Overall, I find writing fiction torturous. All writers say this, obviously, but I’ve come to realize that they usually mean the “writing” part: They can’t stop daydreaming long enough to put it on the page. I love the writing and hate the imagining, which is why I churn out 50 dry essays for every nugget of fiction.   

...

And, suddenly, fiction clicks. Paty says I used to worry that “I feel like I’m doing reading wrong.” Descriptive language in novels was important to her but impotent to me; I skip it as reflexively as you skip the iTunes Terms of Service. Instead, I scour fiction like an archaeologist: Find the bones.

The slender, olive-skinned man brushed the golden locks out of his hazel eyes. He was so focused on preparing for the assassination that he burned his tongue on the scalding cuppa joe (hazelnut, light cream).

That becomes: There’s an assassin.

I hurdle over paragraphs and pages, mowing down novels in one night because—while others make love to the olive-skinned assassin—I’m just fucking his skeleton. Some books are so fleshy they’re opaque: Lord of the Rings numbs. But Lord of the Flies gnaws, because I could meditate on the idea of society-gone-wild forever. Animal Farm is awesome. 1984. The splendor of Hogwarts is lost, but the idea of a dementor is brain fuel. And 2 + 2 = 5.

Nobody likes an author who shows off, of course. But friends tell me it is the written imagery—when done well—that delivers the very joy of reading. I can’t understand that, but I finally understand this: You really are annoyed with the actor in 50 Shades of Grey. It’s really not how you pictured him in the book.

...

I’ve always felt an incomprehensible combination of stupid-smart. I missed a single question on the SATs, yet the easiest conceivable question stumps me: What was it like growing up in Miami?

I don’t know.

What were some of your favorite experiences at Facebook?

I don’t know.

What did you do today?

I don’t know. I don’t know what I did today.

Answering questions like this requires me to “do mental work,” the way you might if you’re struggling to recall what happened in the Battle of Trafalgar. If I haven’t prepared, I can’t begin to answer. But chitchat is the lubricant of everyday life. I learned early that you can’t excuse yourself from the party to focus on recalling what you did 2 hours ago.

So I compensate. Ask about Miami and I’ll tell you, almost to a syllable:

I didn’t love it. It’s very hot, the people there aren’t ambitious at all. Also everyone is kind of angry, there’s like a lot of road rage. It’s fun to visit but I basically went as far away as I could for college, ha ha.

Facebook?

It was awesome getting to be there in the early days. I remember I would practically run to work in the mornings because I was so excited to share ideas with the team. There’s really no better feeling than seeing someone in a coffee shop using your work.

These lines are practiced. They are composites of facts I know and things I’ve read. I perform them out of body, with the same spiritual deadness that you might recount the Battle of Trafalgar.

And if you ask about my day, there’s a good chance that—having had no time to prepare—I’ll lie to you.

It is hard not to feel like a sociopath when you’re lying about how you spent your Monday and you don’t even know why. And there is a sadness, an unflagging detachment that comes from forgetting your own existence. My college girlfriend passed away. Now I cannot “see” So-Youn’s face or any of the times we shared together.

I have, in fact, no memories of college.

I once proposed to Paty that, since we were visiting my brother in DC anyway, let’s train over to the Big Apple and see Les Misérables. She said, we did that last year—for my birthday.

Often I ask my oldest friend to tell me about my childhood. Stephen and I joke that we’re the couple in The Notebook, but there’s an undercurrent of: Am I an idiot?

I’ve always chalked this up to having “bad experiential memory,” a notion I pulled out of thin air because “bad memory” doesn’t fit: I can recite the full to-do list of software I’m building. On a childhood IQ test, my best performances were on Coding and Digit Span, both memory-driven. Given an increasingly long string of random numbers, I hit the test ceiling by repeating and then reversing 20 digits from memory on the fly. My three worst performances were on Picture Completion, Picture Arrangement, and Object Assembly. I couldn’t put the damn images in order to save my life.

Perhaps none of this is aphantasia. But when I ask a friend how he how-was-your-days, he gives me a tour of the visualizations in his mind. The spaghetti bolognese; the bike ride through the marsh; the argument with the boss, and the boss’s shit-eating grin, and gosh how I’d love to punch him in the mouth, and can’t you just see it now? He says that looking back on his life is like paging through a Google Image search sorted by “most engaging.” He tells me that when he’s on the road, and loneliness knocks, and the damn Doubletree bed is a little more wooden than usual, he replays the time they tried to make sushi together—but the rice kept falling apart!—and we couldn’t stop laughing!—and did you know it burns when sake spews out your nose?—and that’s when she feels closer.

I wonder if it’s why I have such an easy time letting go of people.

Apologies for quoting all of that, and it's not quite an answer to "how do people with Aphantasia read texts and process while studying?", but what Blake wrote resonated pretty deeply with me -- I'm partially aphantasic, strong on conceptual imagination but a lot weaker than most on visual-auditory.

I wonder how that relates to visualizing the development of chess positions. For me it's kind of in-between imagination and just seeing the board as is (and I seldom can imagine it beyond one exchange of moves).

Also, imagining "trivial" things like sitting on a riverbank with a fishing rod is easier for me than imagining things from, say, a dictionary of botanical terminology. It has always been a pain to the extent that I can't describe leaf shapes etc. like they are supposed to be described, beyond the elementary level. But that might be a different failing, an inability to sort things accurately. For some reason, I can still use identification keys which require one to choose between several options, even when the key says "the combination of features is different". I guess people make them as easy to follow as possible, stripping the vocabulary to the basics.