Inspect the handle and locate where it fastens. On some models, the screws may be hidden beneath beauty caps where the handle attaches to the surface of the door. On other models, the screws may be on the inside edge of the door.
Pry off the beauty caps that hide the screws, if they exist. Use the blade of a standard screwdriver to gently pry around the edges of the caps until they are free from the handle.
Remove the screws from the handle using a Phillips screwdriver or a nut driver, depending on the type of the screws. Inspect the screws thoroughly. If they look stripped or otherwise damaged, take them to a hardware store and purchase replacement screws.
Insert the screws through the handle and into the screw holes in the door. Twist the screws several turns by hand to ensure they are threaded correctly. Tighten the screws securely using a Phillips screwdriver or nut driver, depending on the type of the screws. Do not over-tighten the screws, but ensure they are snug. Snap the beauty caps back in place for handles that had them.