To install kojo-ai, download (from below) and run the installer for your platform. Then (re)start Kojo to activate kojo-ai. When Kojo comes up, you should see a message in the output pane telling you that kojo-ai is available.
To play with kojo-ai, download the examples zip file and unzip it anywhere. Then from within Kojo, do a File -> Open, go into the unzipped examples dir, open up the different examples, and run them...
If things don't work on older Windows (7 or later, 64 bit), make sure that the C++ redistributable (64 bit) is installed.
If you want a Mac version of kojo-ai, just open an issue.