Simply visit our discord found here and search for your in-game name in the #connection-events channel for ARK:SA.  Copy down the number displayed after EOSID.  Alternatively, players can press f2 while in-game and copy the EOSID number in the lower right hand corner of the shop UI.  Place this number in the box during checkout that says, "EOSID Number (visit the #connection-events channel is discord and search for your username.)" and press continue.