Your best bet is to archive the install and restore it to the different location.
-Hit the blue menu in Impulse, and go to 'Preferences...'
-Under 'Folders', change the 'Install Locations' drop-down menu to 'My Games'.
-Click the 'Change' button, and point to where you want the games to end up.
-Click 'OK', and find the entry for the game in 'My Games'.
-Right-click on it, and chose 'Archive Installation'.
-Once that is done, uninstall the game.
-Hit the blue menu again, and chose 'Restore archive...'
-Pick the archive you want to restore, and once it's done, it should be in the new location.