Help! Not very computer savvy...

[Subeternal]

Alright try downloading 7-Zip from Cnet or some other reputable site. Its free and should work for these files. Right click the file after installing the program and use "Open with" and find 7-Zip from the program directory and click on it before clicking "ok".

Otherwise you can open the program and look for the file in the directory and unzip it that way.