It's a matter of personal choice what lifestyle you are going to adopt. Some people learn about Polyamory from friends or loved ones or by reading books, either fiction or non-fiction, on Polyamorous themes. Some people belong to religious groups which allow and/or encourage Polyamory. Some come in contact with national or local secular Polyamory organizations. Of course, many people create Polyamory out of their own thoughts and feelings when they first spontaneously discover their own capacity to love multiples.