How to download Frostwolf server?

I downloaded the client from the website : Mist of pandaria via uTorrent.
It downloaded directly to my DOWNLOAD folder.
Now when i want to open the wow.exe this error comes :

Data/enGB/wow-update-enGB-18273.MPQ: World of Warcraft can’t make a required change to an archive file. Be sure you have write permission for the World of Warcraft folder or try running the game in administrator mode. For more information, see: https://battle.net/support/article/6910

what is the problem ?

http://i.imgur.com/5wWKUL6.gif

i got pass that but it stopped me when i tried to login i'm on 5.4.8 am i on the wrong patch if i am how do i change it and to what, thank you