Navigate to 
Grand Theft Auto V > mods > update > x64 > dlcpacks
and drag and drop the folder (superman2) into the location of the directory

Next navigate to:
Grand Theft Auto V > mods > update > update.rpf > common > data > dlclist.xml
and add new line:
dlcpacks:\superman2\

Note: The Suit .ini that is given to you in this zip file is needed for sounds and props to work.