Go to this link to begin and register your account. Be sure that your information that you submit is valid.
First: Register your account
Second:modify C:\Program Files\World of Warcraft\Data\enGB\realmlist.wtf or C:\Program Files\World of Warcraft\Data\enUS\realmlist.wtf to set realmlist list.eternion-wow.com
Delete Cache & WTF folders from C:\Program Files\World of Warcraft\Data
Wait 2-3 minutes for database to add your account.
Alternately, you can download the Eternion-WoW launcher and use it to launch WoW. It will automatically adjust your settings so you can connect to Eternion servers.