If you have the official 4.8 Aion Client (EU) installed, you need to download and apply our patch. After that you can start the game with the "Beyond Aion" desktop shortcut. Otherwise, you have to wait until we have uploaded a full 4.8 client, because our server is still on version 4.8 and the official one is on 4.9.
//edit:
All necessary information can now be found here now.