I had virtually no dating experience prior to deciding to explore being poly. At that point I had been with my husband for 4.5 years and married for two.
I met someone on OKC. We messaged back and forth for awhile, and then met in person. We clicked really well and decided to get together again. At the end of that night, he asked me what I wanted out of our relationship. It was a terribly awkward conversation, but it was the first of many where we asked each other what we were to each other. The next time we got together, I asked if we were boyfriend and girlfriend, for lack of a better term. He agreed we were and that was that.
When in doubt, ask. Actually I think that is probably the fundamental advice for being poly, on all subjects.