Get the Samyang 14mm and 8mm fisheye Lightroom profiles (and other hard to find / install profiles) using Adobe’s Profile Downloader. Here’s the link: http://www.adobe.com/support/downloads/product.jsp?product=192&platform=Windows
Looking for a lens correction (defish) profile for a Samyang 8mm fisheye?
You can find one here: http://akry.livejournal.com/781417.html
On Windows machine, put here: C:\Program Files\Adobe\Adobe Photoshop Lightroom 4.2\Resources\LensProfiles\1.0
On Mac machine, put here: /User (user name)/Library/Application Support/Adobe/CameraRaw/LensProfiles/1.0
The profile is built for use with a 7d. If you have a different camera, you can open up the file (.lcp) and replace ‘7d’ with your camera model (find all instances of ‘7d’). I haven’t tried it as I use a 7d.