Turn off the water supply if needed and clear the area under the sink
Place a bucket or towel under the drain area
Remove the old drain assembly if replacing one
Clean the sink drain opening and remove old putty or sealant
Apply plumber’s putty or the sealant recommended by the drain manufacturer around the drain flange
Insert the drain flange into the sink opening from above
From below, install the rubber gasket, friction washer, and mounting nut
Tighten the mounting nut evenly until the drain is secure
Wipe away excess putty or sealant from around the flange
Connect the tailpiece to the drain body
Install the P-trap and connect it to the tailpiece and wall drain
Tighten all slip nuts by hand, then snug them with pliers if needed
Reconnect the dishwasher drain hose if applicable
Run water and check for leaks at every connection
Tighten leaking joints or reseal the drain if necessary