Remove old caulk with a utility knife or caulk remover
Clean the area thoroughly with soap, water, and a mildew remover if needed
Dry the tub and surrounding surfaces completely
Tape both sides of the joint for a clean line
Cut the caulk tube tip at a 45-degree angle
Puncture the inner seal of the tube
Load the tube into a caulk gun
Apply a steady bead of caulk along the seam
Smooth the bead with a caulk tool or a wet finger
Remove the tape before the caulk skins over
Wipe away excess caulk immediately
Let the caulk cure for the recommended time before using the tub