just a quick thought, but you might want to make sure you have a hydrometer/refractometer, test kit and lighting for the tank. Also, I highly recommend a protein skimmer.
About the water, since this is the first time water is going into the tank you can mix the salt in the tank, but this might stir up the sand too. In the future though, it's definitely better to mix the water and salt in something else (5gal bucket, huge rubbermaid tub, etc) and heat it/aerate it for at least 24 hrs before it goes into the tank. hope this helps.
SD
About the water, since this is the first time water is going into the tank you can mix the salt in the tank, but this might stir up the sand too. In the future though, it's definitely better to mix the water and salt in something else (5gal bucket, huge rubbermaid tub, etc) and heat it/aerate it for at least 24 hrs before it goes into the tank. hope this helps.
SD