I've downloaded the files for the Wrath of the Lich King server, edited the realmlist files to add:
set realmlist logon.warmane.com
set patchlist logon.warmane.com

And checked my client version, and it's the same version as the server, but when I attempt logging in with my account I get this error message: http://prntscr.com/krjdfx

Please help?