GameWith.Us is really intended for people to play games with friends they invite into their groups. I don’t think there’s a ton of value in connecting strangers — you can do that by joining random matches in the games, you don’t need a web site to do that.
When you sign up to the site, the first thing you should do is either join one of the dozens of existing groups, or start a group of your own and invite your friends into it. You can make private groups, where you must authorize others before they’re accepted into the group, or you can make it public so people can just click, join and be admitted.
Just Play …
I could go on and on, but just check out the site: http://www.gamewith.us/