Hello and welcome
There are no rules, as far as i know. However, there are two things you should always keep in mind:
First: be very careful about what personal info you share. There ARE freaks out there.
Second: Keep it safe, sane and consentual and don't do stuff you don't want to do just because someone tells you 'that's what little girls are supposed to do and if they don't they're not good subs and btw i'm a Dom so you better start doing what the heck i tell you' or any such crap.

Apart from that, the only rules that apply are those you set up yourself.

Where you should start? Hmm, browsing the forum, reading threads that interest you, talk to people in the chat, read stories on the library, join the tasking society, ask questions, asf aso, there's so much to do and learn.

And don't hurry, but enjoy and have fun.