WinRAR is for extracting files from an archive. To actually USE a hack, you need to first extract it with WinRAR, then run whatever executable (.exe) is included, unless it's an injectable hack, in which case you'll need Winject or some similar program(Winject is my favorite) to inject the DLL (.dll) into the game file while it's running.
Make sure your hacks are undetected otherwise you will be banned from matchmaking in MW2.