The files will be installed to /Applications/Kognat by default, you can find the uninstaller there.
The folder /Library/OFX/Plugins will be created if that folder does not exist.
A symbolic link will be created from the files in the /Applications/Kognat folder to the /Library/OFX/Plugins folder
This is why administration privileges are required to place the files in /Library/OFX/Plugins this is the location that is scanned by all application for OpenFX plugins.
When you start your OpenFX compatible application, the symbolic links will be scanned and the plugin will load
You will see Rotobot_Segementation and Rotobot_InstanceSegmentation on your menu with the Kognat menu item.
Connecting a piece of footage as input to the plugin will detect things in a variety of colours, as you tick the checkboxes, those class will appear in red green and blue for as many classes as you choose.