If you don't know how to use this, download a DLL injector.
(Some Popular Ones: Extreme Injector, Winject, PerX, DC Injector)
If you're using this on IW5M, you MUST Auto-Inject this. If you don't controls will unbind or you'll be unable to shoot normally.
The only other alternative to this method is to inject it on a "Run In Safe Mode?" prompt. In this way, you will not need auto inject but simply to inject it here and click "No"...or "Yes".
You may find Extreme Injector here.
eg. Download Extreme Injector 2.1, Click Settings, Under "Injection Options" check the Auto-Inject box. Then click Ok. In the "Process Name" box, write "iw5m.dat" or "iw5mp.exe". Yes you can rename the iw5m.dat to iw5mp.exe to avoid updates. Now just start IW5M.
You won't need to do this for TeknoMW3 as additional patching isn't needed.