Welcome to our forum.
Natja's advice is good; follow it and you will be off to a good start. Also you can benefit from reading various other threads on this site, and posting if you have any thoughts or questions. The Life stories and blogs board
might be a good place to start, you can learn first hand from other people's experiences (as well as start your own blog if you want).
Poly relationships are often rocky in the beginning. If you can get through the first couple of years, you'll find that it gradually gets easier.
I wish you the best of luck and love in this new venture.