Clean all dirt and debris from the surface of the wall around the shower-bathtub combo using soapy water and a cloth. Rinse with a damp cloth and let the walls dry completely before proceeding.
Squeeze the adhesive out onto the wall and trowel it smooth, holding the trowel at a 45-degree angle.
Apply adhesive to the back of the surround and trowel it smooth, holding the trowel at a 45-degree angle. Let the adhesive set for five to 10 minutes.
Press the surround into place, applying enough pressure to get a good grip on the adhesive. Install the remaining panels if necessary.
Install the shower head and faucet, or faucets, through the pre-drilled holes in the tub surround. Tighten the connections with a pipe wrench.
Load a tube of silicone caulk into a caulk gun. Lay down a bead 1/4-inch wide over all seams and around the shower head as well as the faucet and handles. Let this cure for at least 24 hours before using the tub.