After downloading and moving Kaleidoscope into the Application folder, you are ready to configure it to work with Tower. First you need to navigate to the Integration section in the Welcome Window.
The ksdiff tool can now be setup by clicking the "Install Now" button.
In Tower, choose Tower > Settings…
Navigate to the Git Config section. Select Kaleidoscope as Diff tool and Merge tool and make sure that "Perform directory diff" is unchecked.
And that's it, you're all set to start using Kaleidoscope together with Tower.