Brush the concrete clean on the existing wall. If necessary, use a flat chisel to chip off any concrete buildup that would prevent your water stop from making flat and even contact with the surface.
Open your can of water stop adhesive and paint the center of the wall with it. You only need a strip about an inch wide; if you apply the adhesive with the very edge of your brush you will get the right width.
Unroll your water stop and cut the length that you need to go from the bottom of your wall to the top. Leave a little extra on it to be trimmed later. You don't want to cut it so the bottom edge of the water stop ends at the bottom, but has a few extra inches attached to it so it turns onto the foundation
Peel the release tape from the adhesive edge of the water stop. One edge only will have a kind of wax paper tape on it to protect and prevent the adhesive on the water stop from drying out.
Hold your water stop up to the top of your wall. Press the edge with the adhesive into the adhesive you painted on the wall. The water stop attaches to the wall at its narrow edgel. Nail the water stop to the concrete with a hammer and concrete nail so it does not peel free while the adhesive is setting.
Continue pressing the edge of the water stop into the adhesive and nailing it every three inches.