Remove the old drain assembly
Clean the drain opening and surrounding surface
Check the bathtub drain size and thread type
Apply plumber’s putty or silicone to the drain flange
Insert the drain flange into the tub opening
Thread the drain body into the flange from below
Tighten the drain securely with a drain wrench or pliers
Attach the drain shoe and overflow assembly if needed
Connect the drain pipe and trap
Tighten all slip nuts and connections
Wipe away excess putty or sealant
Fill the tub and test for leaks
Tighten or reseal any leaking connections