Welcome to our forum.
I guess the best approach would be to tell your wife, "I have something important I need to talk about. When would be a good time for you for us to have a sit-down together?" Then, when the appointed time comes, tell her, "I have been reading and studying about polyamory and I am interested in it. Can you tell me what your feelings are about it? Perhaps you could take same time to read and learn about it and get back to me?"
Some good sources of "starter info" are:
Polyamory is all about love in general, but sex is usually a part of that (and is the reason why most people have a hard time wrapping their mind around it). As far as I can tell, your post makes sense, and you just have to look for ways to explain it to your wife. It sounds like there's a good chance that she at least partly understands the idea.
Just let us know if you have more thoughts, questions, and/or concerns.