Wasn't working for me and was dying to figure out how to work it but I finally figured out how to get it working!
Been using it for 2 days now.
1. Open up the wallhack folder (oshbpcodmw3)
2. Open the CONF file (oshcodmw3) with Notepad and change to the following settings:
3. Open up FInject (download it if you don't have it) and select the .dll in the folder
4. Type in the following process in the box: iw5mp.exe
5. Start up MW3
6. At the MAIN MENU... alt+tab and inject the .dll and alt+tab back into the game
7. Start playing
The first time you try to join a game, MW3 will crash on you but just reopen MW3 and reinject and you should be fine. I follow these steps to get it working. Hope it works for you too!