As you install it pour 3-4 gallons of water into the brine tank unless there is water in it. If so then watch you don't overflow the water on the floor. If there is no salt in the tank, add 40 lbs. After it is installed, add 1/4 cup of non-scented bleach into a quart of water and pour that into the water in the brine well in the brine tank. Then do a manual regeneration. That is to regenerate the resin and sanitize the softener.
You can go to the following link and their animations to see how a softener works.