Hiya, Stella! Nice to meet you! I'm Jackles and I'll be your tour guide for the next paragraph. XD
Just to add on what to Cec said :
Classes: When you applied, you picked your classes. Just try to post in each class and you should be good. Right now, I think they are reconfiguring.
RP: The best thing to do is just post! But, you can also check
Roleplay Request and
Character Plots to plot with people and request threads.
Friends: The best thing to do is keep an eye out for potential friends. Fifth years (and especially ones in Hufflepuff) may be your best bet. Then, PM the person and ask to develop the relationship. Sometimes, you can also ask to have an established relationship. Say I had a fifth year Huffer, I'd message you saying "Hey, I read your application and our characters seem like they get along. Since they are the same House and age, could we perhaps say they met during their first year and have been study buddies and close friends ever since?"
House Points: They can also be given for keeping a class going or having creative plot twists. The best thing to do is stay active in classes.
That's all I have to add. If you have any questions, our wonderful admins (the ones with baby blue names) can help you or you can PM me 'cause I have nothing better to do. XD