You’ll need to refill the salt. That’s it. Most systems have a little window so you can peek at the salt level. Don’t let it run dry! The resin beads inside the tank will get gummed up with minerals, and then you’re calling a technician.
Once a year, clean the brine tank. Dump out old salt, scrub any sludge (it looks like wet cement), and refill with fresh salt. Some systems also need a resin cleaner every 6 months to remove iron buildup. Follow the manual, but it’s not complicated—more like changing your car’s oil, but fewer greasy hands.
Oh, and if you have a drain line, make sure it’s not clogged. Otherwise, the regeneration cycle will flood your floor. I learned that one the hard way. Let’s just say my cat was not impressed.