GD Library allows image manipulation and it is a minimum requirement of EasySocial. This allows the scripts to manipulate, resize and create image files on the site.
Installing GD Library using YUM (linux)
To setup php with zip library on Linux, it's pretty easy since everything can be done using YUM. Those that are unfamiliar with YUM should start utilizing it. You can learn more about YUM on WikiPedia.
Enabling GD Library (windows)
To setup php with gd library on Microsoft Windows machines, you only need to edit the
php.ini file which is normally located in
C:\Windows\System32\php.ini. The folder may differ and you can find out the loaded php.ini configuration file via the PHP Information in Joomla.
Restart your IIS / Apache and you are good to go!
If you are unsure how to do this, it's best to contact your hosting provider for clarifications.