Unzipping for newbies?

[Tomfirth]

Hi all, sorry if you've had this question before, but here goes.

I am trying to get a new custom skin onto eq2.
I downloaded the file and understand the instructions, however i have one problem. In the install faq, it tells you to unzip the file.......how do I do this, I don't have any experience in this kind of thing.
Thanks for any help.