After cloning the repository, on the KiCad main window, Go to 'Prefrences' -> 'Manage Symbols Libraries' and then in 'Symbols Libraries' window, Click on little folder icon below the list and select .pretty folder of each footprint library you wish to add.
Almost like how you add symbols libraries, On the KiCad main window, Go to 'Prefrences' -> 'Manage Footprint Libraries' and then in 'Footprint Libraries' window, Click on little folder icon below the list and select .kicad_sym file of each symbol library you wish to add. e.g: HadiKiCadLibrary\Symbols\Connector - USB\Connector - USB.kicad_sym
on KiCad main window, Go to 'Prefrences' -> 'Configure Paths' and add a new path to the list. Set the name to 'KICAD_USER' and the value should be THE PATH ON YOUR COMPUTER WHERE YOU CLONE THE REPO\HadiKiCadLibrary\3D Bodies