Can't open ".app" to lunch wow of find "installer" Help pls!

Hey,
I'm currently running this..
OS X El Capitan Version 10.11.2
MacBook Pro (13-inch, Mid 2012)
Processor 2,5 GHz Intel Core i5
Memory 4 GB 1600 MHz DDR3
Graphics Intel HD Graphics 4000 1536 MB

I have recently downloaded "Wrath of the Lish King 3.3.5a (old)".
But i can't open the .app to launch wow. any suggestions how to fix?
the error says: The application "World of Warcraft" can´t be opened.

I tried to fix it by following this ticket:
http://forum.warmane.com/showthread....t-launch-3-3-5!
However I can't find the "installer" file inside /contents/MacOS/.

Any suggestions on how to solve this problem?
Thanks in advance.