Hi Debby, We are sorry that you are experiencing a problem with your faucet. The handle on the model 9159T-DST faucet is held on by a set screw. The screw is located underneath the button opposite the lever portion of the handle. You will have to pry off the button with your fingers to access the screw. Once the handle is positioned on the cartridge assembly, use a 1/8" allen wrench to tighten the screw onto the cartridge. Here is a link to the parts breakdown to help with your repair.http://www.deltafaucet.com/customer...