Making friends in grad school at 21 years old??? Advice please

I did college classes in high school so I graduated undergrad early and will be attending grad school this fall at a somewhat small university. I’m 21 years old so most students my age will be undergrad and already in established friend groups. I do have one very good friend there that I will be roomates with plus two other girls who I have not met yet (they don’t seem like my cup of tea tho lol) anyway I am mutuals on instagram with some students there and they seem fun ppl to be friends with. To get to my question, I need advice on how to become friends with some people if they are already in established friend groups. I am coming from undergrad where I had very good group of friends and many aquaintances in which we would party and just hang out very often and I do not want to lose that that type of thing. It was easier to establish my undergrad friend group because everyone was new and everyone just wanted to be in a friends groups (we became friends by going to a frat party and we hung out all the time since)