I am a new player. I downloaded the installer from this website for Mist of Pandaria expansion. The first time I login my account, I wasn't able to push it through so I did a little search in the forums and fortunately found the solution.
For new players, if you have issue logging into your accounts, try:
1. Opening your game / client folder
2. Open WTF folder
3. Edit Config.wtf file via code editor (notepad, notepad++, vscode etc.)
4. find the line ```SET realmlist "logon.warmane.ru" ```
5. replace "logon.warmane.ru" with "logon.warmane.com".
6. Ctrl + S to save
7. Start the client