Which terms are you unfamiliar with? Which certain techniques are you uncertain with?

As you've been told in the CB already, you need a C compiler that can compile the XS extension, because GD is not a pure Perl extension but relies on a C part. I've pointed you to our Tutorials, A Guide to Installing Modules and Installing Modules on a Web Server.

If all you want is to resize JPEG pictures, often there is the jpegtrans tool suite (cjpeg and djpeg) installed which you can run as command line tools to resize images without compiling anything.