ImageMagick MOGRIFY

Does anyone knows how to use ImageMagick software, and more specifically Mogrify?

With Mogrify you can manipulate graphics using the command line. But I have never used Mogrify and I can’t get it to work. I downloaded and unzipped the ImageMagick package but can’t get to work Mogrify.

Do I need to do more that unzipping? How can I use Mogrify using the command line?

Please help!

Leo