RP's advice is always good. There are no set rules on how things must go, but there are some good guidelines:
1) There are no set rules on how things must go, but there are some good guidelines. (This is important enough to repeat, yes.)
2) Communication is critical to any successful relationship but especially to poly folk.
3) Be proactive and honest with your communication.
4) New relationship energy (NRE) can cause toxic overdoses. Funnel some of that energy into preexisting relationships to avoid blinding yourself or having them feel ignored.
5) Talk to your existing partner about a new person before talking to the new person. This shows you care about the existing partner and avoids surprises. (You're not bringing home a new fish, after all.)
6) Adapting to life as a self-identifying poly takes some adjusting. That's true for your partner, too. Give it time and know that it gets better.
7) A poly's love may be able to grow unbounded, but the clock has limits. Managing your time can be more important than managing your heart.
8) Have fun.
As for finding other poly folks, there is info on events in these forums, meetup groups, and all sorts of ways to connect on the web (OKC, OkCupid, is a common point if reference). If you have specific questions, a problem, or a specific situation, post here, and someone will chime in--or many someones. Recognize that this online community is often blisteringly blunt. Expect some tough questions if you need help getting through tough spots.
For reading here, I'd suggest tags of interest and the "Life Lessons" thread to start.
Best of luck.