You have to extract the cracked files from the rar-archive.
For that you can use WinRAR (
www.rarlabs.com).
After extracting the files, you will have an exe-file (most of the time).
This EXE-File you have to copy to the folder, where the game is installed.
Windows will ask you, if you want to overwrite the already existing file. Just click YES!
That's all!!!