Since hard water creates mineral build up and residue, water softeners keep that from happening. Water softeners work by adding salt to your hard water. The process creates soft water which dissolves soap more easily than hard water. If your water softener runs out of salt you will have to add more and restart the machine.
Turn off your water softener.
Remove the salt keeper from you water softener and add more water softener salt to the keeper. Make sure the keeper is almost empty before you add more salt to it.
Pour 3 gallons of water into the salt keeper to help dissolve the salt after you added it.
Turn your water softener back on.