I’ll play as either side, OOB rules with or without a bid

I’ve been playing a lot of TripleA against myself just to practice for in-person games, but I’ve gotten really into it and I would like to play online.

My only problem is I’m not quite sure how. Where do I go to do that? How much time do I need to have set aside to play a game?

Any help would be great!

When you build into an occupied sea zone, what must your opponent decide to do on their turn? Are their options to leave the sea zone or to remain and fight? Or can they remain there without fighting?