Alright, go to the combat arms hack section scroll down, and select a working hack. Download it to your desktop...
Get a injector...i personally user perX, has never failed me before.
Run PerX as admin, Then make sure the process is Engine.exe
then click browse and select the hack you downloaded..it will be a .dll.
Then run combat arms, and have fun. If its a menu hack the open menu button is usally insert.