You need to either have a GM with the iGM module running in listen mode whose IPA you know, or you need to find a gme being hosted by a GM on the RPGRealms website and connect to the game via that matchmaking client to the GMs iGM module.
I'd tell you how to do that but I have never done it, so I do not know.
Their website does not actually host any games, it is just a meetpoint for those gaming.