PH 6.8 or 7.8? You have a typo.
Your FC is dangerously low. Here's what you need to do:
If you've not been adding a ton of bleach or anything else to bring salt levels up, it's safe to say you have none. I would still at least let a pool store test your salt if you don't have strips or a drop test, but if you haven't added anything, your water won't naturally have any salt in it.
Your SWG will say how much salt it needs. Usually they operate in the 3200 to 3800 ppm range, with a minimum of 2500 and a max of 4500. But read your manual for your particular unit and it will say. Using pool math, punch in the gallons of your pool, and the current salt level of 0. Shoot for the lowest your SWG likes at first (you can add more later, but you have to drain water to remove if you add too much). Add the bags of salt around the perimeter of the pool. Brush to dissipate. Don't just dump it into the skimmer.
Your CYA is zero so you will need to get that up. SWG's like in the 50 to 80 range. I usually run mine lower just so if I ever did need to shock the pool it wouldn't require so much Bleach. 60 or 70 is a good safe number. But like salt, shoot low to start with as to remove CYA you have to drain water. Since we are going to be doing a OCLT at some point, let's target 30 for your CYA right now. So, using pool math again, enter 30 for your CYA. That's enough to get you started. Add the required granular stabilizer (CYA) in a nylon sock and hang it in front of a return. Squeeze it periodically over the next day to help it dissolve. Once you put it in, don't test for it until at least a week because it takes that long to fully dissolve and show up reliably on a test. Just assume you have 30 CYA going forward.
Now, you need to add Bleach. Using pool math and the CYA/FC chart
Pool School - Chlorine / CYA Chart target 4 to 5 for your FC. Using Pool math, add enough liquid bleach 8.25% to reach your FC level. Unlike CYA and Salt, better to overshoot a little on FC than undershoot and allow algae to grow.
Lastly, verify your PH. If it is 7.8 you're on the edge of acceptable. You can add a little Muratic acid to bring it down to 7.5. If it's 6.8, you need to bring it up with some baking soda. 6.8 is much worse condition than 7.8 so important that you tell us what your pH is.
After you add the Salt, CYA and Bleach, let all this circulate for two days. Keep testing your FC and keep it at 5 or slightly above. I'm concerned that with your low FC right now you may have algae starting, so better to keep your FC up right now.
After a couple of days if your pool remains clear, do an OCLT test. Here you will be verifying that you don't lose more than 1ppm of FC overnight. If you don't then you don't have algae or other organics growing. If you do, you need to SLAM (follow pool school).
If you pass OCLT, then add the remaining Stabilizer (CYA) to bring your level up to 60 or 70 and turn on your SWG. Monitor your FC for the next few days to make sure your pump and SWG output is sufficient to keep your FC above 5. Add bleach if you need to subsidize.
After a few days, test your salt level again and add a little more to bring it to the nominal range of your SWG.
Welcome to TFP!!!
