I think most of the useful advice concerning polyamorous relationships and their unique challenges, etc., is universally useful. But some of it concerns unique or particular situations or conditions. I don't have enough experience with heterosexual loving relationships to feel that I'm familiar with the nuances of those which differ from my experience as a queer man. (I'm bi-, and although I had a brief loverly relationship with a woman, all of my long term loves have been male.) So, I'm hoping the poly heteros in here will chime in with guidance for you and your two women lovers.
Anyway, there is tons of stuff on polyamory to be found on the internet. Try a www.google.com
search of polyamory, polyfidelity, V.... Also, there are a bunch of books on the topic, and some of them are mentioned and discussed in our topic in here on books, magazines, websites....
I'd be happy to answer any particular questions which you may have about polyamorous practice -- though it will all be uniquely from my perspective. I think most of the insights I have on the subject probably apply to all sorts of configurations and gender mixes.
Do your lovers experience any jealousy toward one another, or fear of loss, insecurity..., related to your non-conventional lovestyle? Are there particular problems which need addressing?