Firstly, have you opened the menu correctly? - LT and X or B (It's different on Fenix menu).
If not, I'd suggest using a patch called Project Iconic v3, it's a free patch and can be found on here in the download section, it's the same as jiggy menu or something to open, so it's LT and Knife. The menu is alot easier than Fenix no offence to the guy/girl! I get confused with it, and does my head in as X is the go back button!
How to install?
Firstly you will need the modded default_mp.xex and the Tessaract.dll file, oh and the TU18 for BO2.
RIP/Burn/Copy Black Ops 2 to your HHD or create another copy of the game if you already have it!
Move the default_mp.xex and Tessaract file into your game, also move all the files within the TU18!
After that, create a ("Raw") folder within the game, move the "Maps" folder you would of downloaded from the patch Fenix or Project Iconic.
Back out after it's copied the maps folder into the raw folder.
Load up default_mp.xex and back out, load up zombies! and off you go! It's LT and Knife.
Hope this has helped alittle, if you're still confused and it's not working! hit me up with a PM! I'll be happy to help you, as I know the struggle when you first start off!