Have a look at this post it has some guidance:
old post about images
But you probably dont need to install it, most hosts have it installed.
If you are using cpanel you can check to see which one is installed by going to the left side menu and clicking on "installed perl scripts".
The path to ImageMagick , if you have it will be something lile "/usr/local/bin/convert" or /usr/local/bin/.
The link with the good info is:
http://forums.hostdime.com/showthread.php?t=2091&highlight=NETPBM