Hi mark. Welcome to AA!
First off, since you are just starting the tank, you can add salt after the fact. If your tank was up and running already with livestock, then you would need to mix and aerate it first.
levels vary from 1.021 to 1.24. This seems to be typical for most people. The refractometer was a good choice!
As far as LR
goes, you can cycle the tank with it now. In fact, it is better to add it now rather than later. Just get between 1 1/2 - 2lbs. per gallon and you will have a great biological filtration established.
Last item, for additional information, Robert Fenner has a great book called "The Conscientious Marine Aquarist." This book answers a lot of questions during the setup of the tank, as well as maintenance, fish compatibility, and corals. I personally own this book, and I look at it all the time. HTH