Yeah the Readme is wrong, There is already an admin account but I deleted mine so I dont remember the details or password.
To make a new admin account: just make a new account by going to the included webpage cPanel®
Steps:
1. Make new account
2. In the MaNGOS window you opened, type "setgm (yournewaccountname) 3"
You leave out the ( ) when typing account name, and there are 3 types of GM
1 low power
2 med power
3 omg power
Note: If your having problems when you make new accounts make sure your have the correct client selected.
If your using the beta client then select "Wrath of the Litch king"
If your using the retail up to date client then use "Burning Crusades".