All you need to do to connect to our server is make a new account on the account page, http://legacy.servegame.org:8080/stats/register.php
then go to your World of Warcraft directory/Data/enUS or enEU(depending on where you live)
open realmlist.wtf in notepad, then change it from
"set realmlist us.logon.worldofwarcraft.com"
to
"set realmlist legacy.servegame.org"
Then open World of Warcraft and login!