Make a list of all the tasks you need to do, pick the 'hardest' one first (psychologically hardest for you), and force yourself to just make a start, even if you tell yourself you'll just do 5 mins, it's usually easier to keep going longer once you make that start. Pomodoro technique, 25 mins focus, 5 min break to move about, works well for me.

I would also say be targeted. It's only first year at uni, depending on where you are studying it might not be that challenging or even important to you final degree. Make sure you know how you're being assessed, what the learning outcomes are, and if there's stuff that's new to you, or you're rusty on, spend time learning that. But for things you already know from school, it's fine to just dip in and out, do a bit to reassure yourself you know it well enough, then go socialise, get some exercise, do a hobby, join a student society. All those things are good for you, some can even look good on a CV, and it's likely you'll have to de-prioritise them a bit in later years of your degree, so enjoy the chance while it's there!