This addon is a plugin. You need to extract it to your /plugins folder to install it.
The Flickrizer allows users to add thumbnails from their Flickr account to their Vanilla account profile.
Update I changed the flickrizer so that instead of using the flickr feed url, it uses the id portion of the url only. This was done to prevent the extension from being used in an exploit. Here is an example flickr feed url with the portion required by vanilla in bold: