i am creating a gallery and i want to transfer pictures from classmates own profiles to the gallery. when i try it tells me the extension is wrong (.zip). how do i unzip that file?

Depending on the operating system you are using, you should be able to right-click on the .Zip file and choose to extract the pictures into that folder or a different one.

If your computer does not has a Zip program, you will need to install a program such as winzip to unzip these files. There are some free versions of zip programs available, or I believe that WinZip does offer a free trial.