gvSIG-Desktop 1.12. User manual
From the Tools / Add-ons Manager menu select 'Installation from URL', enter the URL and click 'Next'.
By default the official repository of packages for the current version of gvSIG is shown.
Select the add-on to install from the Official (those that have passed the process of formalizing gvSIG) or the Unofficial tab and click 'Next':
After installation, you should see the following window:
If you go back to the Add-Ins menu you will notice that the add-on has been properly installed.