Welcome to our forum.
Finding people to date in a poly setting is not easy. The others have given some good suggestions; here's a few more.
You can also try googling "polyamory" with the name of your state or city; a link to a local poly group might turn up.
Even if it's not an "alternative" type group, if there's a club or something in your area that does something you're interested in, you can always join that group and it just gives you a way to get out there and meet people. If you meet someone on a platonic level and get to talking about poly, then they can decide how they feel about it without any "pressure to agree." Then if they do decide poly doesn't bother them too much, and some kind of romantic connection subsequently develops, you'll already have "had the poly conversation" with them.
Time and patience are key elements here. Sometimes it's when you're not looking that you find someone.
Hope you have luck and love in your search,