Clear the sink of any water
Look under the sink for the stopper linkage
Find the pivot rod connected to the drain
Loosen the retaining nut on the pivot rod
Pull the pivot rod out of the drain assembly
Lift the stopper straight up and out of the drain
If the stopper is stuck, twist it gently while lifting
Remove any debris or hair from the stopper and drain
Reinsert the stopper by lowering it back into the drain
Reconnect the pivot rod and tighten the retaining nut
Test the stopper to make sure it moves freely