I second Mono's question..............
How is it you believe you ARE poly ? What's brought you to this conclusion ?
I think it's natural regardless of what situation you are in to be 'attracted' to other people. However - 'attraction' does not in and of itself make 'poly' !
'Poly' is deep work and deep understanding of your true inner nature. That stuff takes time.
I think it's a wonderful thing to explore. It's something one should know about one's self. But I'd suggest you DO that exploration before assuming and generating all sorts of complications and drama.
As for breaking the ice once you DO finally get there (assuming you do), it's pretty easy to point to an almost endless list of magazines, books, documentaries etc. Poly is coming more and more to the forefront daily as a legitimate option for many people. There are many references on this forum if you do a search.
Check it out, think it through FULLY as to what it means to you both (remember it could swing both ways - he might fit poly too !) and don't rush things.
Lots of great folks here happy to help with any questions you come across.