Installation is pretty straightforward. Download latest release from OpenNTF website.
Unzip the downloaded file and you should get the following folder structure:
Install content of
designer-updatesite into your Domino Designer via File - Application -Install... menu (and restart DDE afterwards).
Import content of
server-updatesite into update site database on your server (and issue
restart task http command on your server console to load it).
And you are all set to use it.