G'MIC is a plugin Deb; Not sure of your OS or what version of GIMP (32/64 bit) you are running, but you can go the the G'MIC website to download it. Also can go to the Flirkr site for it's primary blog (to get help). I have to add that since I've been using G'MIC, pretty much every edit I do, I use some G'MIC preset. It's that big of deal. It's like giving GIMP a shot of steroids. Very (extremely) powerful plugin yet easy enough to use for beginners too. You can call it a game changer if you will. Once you install it, I hope you find time to get some sleep. lol
http://gmic.sourceforge.net/http://www.flickr.com/groups/gmic/