Gotcha! So, I started a lefty book club with a couple friends, when I was in university. So in that sense, things were easier. But if you're starting with just yourself, you're gonna have to kinda start with boring stuff.
Come up with a name for your book club. Advertise it around campus. Make posters! If you see someone with a leftist sticker on their laptop or something, strike up a conversation!
Get at least 2 or 3 other people on board first. Then, if you're not a big theory-head, see who is. Or at the very least, see who's good at talking to people. Let that person start facilitating discussion. Have a few informal meetings, and see how they go!
You'll start to learn how things will work, the more you do it. This stuff takes practice, and you'll gain a lot of skills doing it, but don't assume it'll all go smoothly the first, or even the 5th or 10th time.
On that same point though, relax and have fun! Everyone is there to learn and talk about stuff.
If you're lucky, you night also develop opportunities to collaborate with other student groups, or community orgs, and do some activism as well. I know with the group I helped start, it grew over time to a full fledged campus activist org that held film screenings, talks, protests, mutual aid, and more. And that's because we kept making ourselves known on campus, and in the wider community, and put in the work to make that happen.
But, also don't feel like you HAVE to grow it that way, if you don't want to. You're free to just let it be a small reading group between you and some friends!
Dare I suggest that the reason for twitter becoming so right wing, is that it's a centralized social media website, subject to the crazed far right whims of the capitalist who bought it...