After downloading and moving Kaleidoscope into the Application folder, you are ready to configure it to work with GitFox. 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 GitFox, choose GitFox > Settings…
Navigate to the Integrations section. Select Kaleidoscope as Difftool and Mergetool and make sure that "Use Directory Diff" is unchecked.
And that's it, you're all set to start using Kaleidoscope together with GitFox.
The Mac App Store of GitFox doesn't support external diff- or mergetools. See App Store and Retail Version Differences.