You can put salt in your pool now with the water temperature below 55F but you can’t run the SWG, so why bother?
Wait until the water gets to about 60F. The salt will dissolve better in warmer water. Then add the salt. Add 2/3 of the salt you think you need and let your pump run for 24-48 hours to dissolve it. Then test the salinity with a K-1766 salt test kit. Then add a bit more salt if necessary.
If you overshoot your salt level you can only lower it by draining. So better to undershoot and then add more.
Once you get the target salt level turn on the SWG.
What brand salt will you be adding?
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