You installed PSOPC (v2), which is a different game entirely. Basically what you need is to get a Gamecube emulator named Dolphin and run EP3 .iso with it.
1. Install Dolphin
2. Download and extract PSO EP3
3. Follow this guide
If you have any additional questions or you need some technical...
I was following Tethealla development because it looked promising, and also because fuzziqersoftware's newserv was kinda dead end back then. And as soon as Ephinea went public, I've made an account on day 1.