Find the instructions on how to install on Mountain Lion on the right side of the Features page, underneath the system requirements.
http://beta.toonboom.com/professionals/storyboard-pro/features
Also, if you are using Storyboard, make sure you have a printer configured following the instructions in the knowledge base:
http://www.toonboom.com/support/kb/questions/411/Mac---Application-performance-issue-when-there-is-no-printer-configured-on-Mac-OS-10.6.3?333