Pry away any old tile and remove switch plates or outlet covers using the screwdriver.
Sand the backsplash area using 80-grit sandpaper.
Wipe area well using a damp rag to remove any dust, dirt, paint flakes or old mastic and grout.
Apply a thin layer of mastic or thinset to the backspash area using the putty knife.
Place the plastic tiles in the desired pattern, pushing them into the mastic or thinset to achieve a good seal.
Clean off the putty knife and allow the tiles to set overnight.
Apply grout to the gaps between the tiles using the putty knife. Push the grout into the gaps as deeply as possible.
Wipe away excess grout using a damp rag. Allow the grout to dry completely, per the manufacturer’s instructions, before using the backsplash.