1) Download hack which should be a .dll files and injector.
2) Open injector (run as admin on Vista by right clicking).
3) Browse for the hack (.dll file)
4) The area in which you type the destination of the injection type in engine.exe (if that doesn't work type engine only).
5) Press inject.
6) Open combat arms.
7) Go in game and there should be a logo in the top left hand corner (press insert to open menu and highlight the hacks you want).