Accomodation Questions

i've been really stressed lately thinking about accomodation and how it works, there's seems to be no straight answers when applying for these kinda things.

I'm 19 now, i come from a troubled background when it comes to places to live and family n such, and the idea of moving away to university is great. But i'm a little confused.

within my application for accomodation, it says once my offer is recieved i have 5 days to pay 400 pounds to secure placement.

main questions really are very generic:

when do you move in?

does student finance cover the costs of living there? (assuming im eligble for the highest ammount)

I don't have my parents in my life to guide me through these things or to be able to fall back on if i don't know these kind of things so, any help is appreciated and my apologies if these questions have frustratingly easy resources to find out about, thank you :)