Locate the damaged section of the seal around the Crestline window frame. Cut this fragment of the sealant on either side using a utility knife.
Pry the seal from the seams with a putty knife for leverage. Allow the seal to come loose and peel off the remainder with needle nose pliers if necessary.
Wipe the exposed seam with a damp cloth to clear out any visible dirt or residue; the Crestline frame can't be properly insulated if there are contaminants trapped beneath the replacement seal.
Snip the nozzle on a tube of silicone caulk and leave an opening 1/4 inch wide or less to dispense the sealant. Puncture the foil seal with a stiff wire or paperclip, then load the tube into a caulking gun.
Draw the tip of the gun along the bare joint in the window frame where the old sealant was removed. Apply consistent pressure on the trigger as you apply an even bead of the silicone sealant.
Glide the back of a plastic spoon or craft stick over the new seal for a neater application, then let it cure over a full 24-hour period.