You need to add live rock for starters, Around 30 pounds should do it. Then you should get a book on how to keep a saltwater aquarium and do plenty of research. You will need a powerhead (possibly 2) a refractometer for measuring salinity, saltwater test kits, a ro
system for making water (no tap water here I am afraid) buckets for mixing water, extra heater/powerhead for mixing water.
what kind of filter is it? What kind of lighting do you have? What are you future plans for the tank? Once you have all these things you can start your cycle, which could take about 4 weeks, then it's time for fish