You should test the salt content of the water after your pool is filled. You probably have 200ppm or so salt in your city water.
Get the pool water chemistry stable using liquid chlorine, acid, etc before adding the salt.
Shoot for the low end of your range when you add salt. Easy to add more.
Circulate the pool, run the brush around, use the vacuum, etc to mix the salt well. Start the SWCG the next day.