Turn off the water supply
Open the shower taps to drain any remaining water
Cover the drain to prevent losing small parts
Remove the tap handles or trim plates
Unscrew and remove the old tap cartridges or valve components
Clean the valve area and remove any debris or old sealant
Install the new tap cartridges or replacement valve parts
Refit the trim plates and tap handles
Tighten all screws and fittings securely
Turn the water supply back on
Check for leaks and test hot and cold operation
Reseal around the fittings if needed