so I moved the downloaded GD file

Just as a summary, for any newbies, who tend not to read the README's and FAQs... :-)

The original manual way of installing a module, which you may have downloaded by web browsing at search cpan ; is to simply unpack it anywhere you want, run perl Makefile.PL, make, then as root, make install

Alternatively, with the CPAN module, you can run as root

perl -MCPAN -e shell
[download]

which will give you a CPAN prompt

cpan>
[download]

at which you would type

cpan> install GD
[download]

then the CPAN module will find the best place to download the current GD module, and will unpack, build and install it from it's CPAN style directory tree in the user's ~/.cpan directory.

Unless I'm in a hurry, I always manually download my modules and go thru the perl Makefile.PL,make,make test, su, make install routine. I do this mostly because I like to have easy access to the module's sources in a single directory, rather have it hidden in the labyrinth of A-Z subdirs used to catalog authors and sources.

Of course there are more difficult to understand refinements, like installing modules to your home directory, instead of su'ing to root to do the "make install". The easiest way to do that, is with the local::lib module, with which you can as a simple user do

perl -MCPAN  -Mlocal::lib -e shell
[download]

then

cpan > install GD
[download]

will install to your own home directory without needing root privileges.