The best place to start is to look in the OOC section of Everfree Empire. I have a link here. There you can find an open roleplay that is accepting characters. Or even start your own!
As for multiple characters, it will be up to the person running the roleplay. I would recommend starting with only one character at a time, multiple can be a hassle to keep posting for two at a time.
And the best part of doing roleplays is doing it with others! Go ahead and look for something you like and ask to join in.
I would also give the rules a read. I have it linked right here. If you have any other questions, you can message me.