Turn the hot and cold water off under the sink by turning the knobs to the right all the way. Open the faucet to let out any remaining water in the lines.
Unscrew the hose from the valve under the sink using an adjustable pliers. Pull the sink sprayer up and away from the sink, pulling the loosened hose out through the same hole. Wipe down the edges of the hole with a damp cloth.
Push the threaded end of the soap dispenser's reservoir up through the hole. Screw the dispenser ring over the threaded end of the reservoir to hold it in place.
Pour your choice of soap into the reservoir until it is full. Lower the pump into the reservoir and screw it into place until it is secure.