From your description you have a backwashed filter and then a water softener with a salt tank.
You add water to the salt tank with a bucket or garden hose. You should put like 5-6" in it but not down through the salt. Move the salt aside or if you have a brine well, it goes down to the bottom of the tank. Most Rainsoft softeners do not have a brine well.
You'll probably have to call a dealer for service because other than some general troubleshooting instructions in the back of a manual, there are no other troubleshooting instructions because all control valve brands are different, so you need specific instructions for your specific brand of control valve. And it is proprietary to Rainsoft.