You will need to drill holes in the replacement handle using a common 3/16" drill bit found in most drill bit sets. You will need to insert the handle into your mop's black brace, making sure that the top of the handle is at the end of the brace. With a dust mask covering your mouth and nose and with safety glasses on, proceed to drill the handle using the pre-drilled holes in your black brace as a guide. Once both holes have been drilled, secure the screw and nuts provided with your replacement handle through both holes.
If you prefer to not have to drill your handle, you will need to purchase a new black brace with your Monster Mop handle. See next item.