I am still pretty new here, so I cannot answer all of your questions, but the first and foremost important thing in a polyamorous relationship is ... of course ... total and complete openness and honesty with your partner(s).
If you have any misgivings, fears, hesitation... or conversely excitement, goals... and if you know what it is you are hoping to get out of this, then now is the time to air these things. Talk the subject until you are blue in the face!
I think such a talk or series thereof can only have positive and reinforcing results.
That may be a little Captain Obvious of me, but... that is what I can contribute for the time being.
37 y.o straight mono male in a V with my soulmate and love of my life, A (31 poly bi F) ... who is a hinge between myself and P (29 straight, mono male)