get yourself out there now, then. start small. say hi to your classmates. if anything, say that you feel like you wish you did more in first year. ask them if they know of any good pubs, clubs or bars (whichever you feel most comfortable with), or look on socials and find an event you'd like to propose going to with some and ask if they want to join. ask your classmates which societies they are in, and express interest to them if they sound fun to you - ask when their next social is perhaps. see if any societies have taster sessions or if there's a society/freshers fair you can attend (normally you don't need to be a fresher to go!). don't push yourself too hard, or it'll end up being more of a chore than enjoyable, and that defeats the point of going to uni in the first place - uni and university are two different things if you want to look at it like that and it's just about balancing the two to your liking. I barely drink but normally my friends and I do an evening cinema trip followed by a cocktail or two where we discuss the film (we love analysing them haha). also asking classmates if they want to join you to get lunch or grab a coffee after class is fine too.