Adobe Photoshop is a Windows app. It has been ported to Mac OSX Snow Leopard, but it will not run in Linux unassisted. To install Photoshop, you need to install Wine and follow their directions to install Photoshop. Start here:http://www.winehq.org/search?cx=partner-pub-0971840239976722%3Aw9sqbcsxtyf&cof=FORID%3A10&ie=UTF-8&q=adobe+photoshop+cs4&siteurl=appdb.winehq.org%2F#1503
This is a listing of results posted by others that have used Wine to run Photoshop in Linux. It will give you an idea of how successful your efforts might be.
You could also install Virtual Box either from Software Manager or from their website, or install another virtual machine program, run Windows in the virtual machine, and run Photoshop in Windows.
The only other option is to dual boot Mint and Windows.