rar are zipped (compressed) files and must be extracted using a compression/decompression program. I use 7 zip for this. It's good and it's free. Get it here.
http://www.7-zip.org/
After you install it, right click on the .rar file and choose extract. Then you can use the files.
For step by step MOD installation, go here:
http://forums.ubi.com/eve/forums/a/t...6?r=9611075206