get live sand and some live rock, add your source of water and salt. Let the tank sit for a while with a piece of table shrimp in it to get ammonia into the tank. This will start your cycle. After ammonia and nitrite hit 0, and nitrate lowers to around 20ppm, preferably 10ppm then you can add your small cleanup crew, and go from there. Fish need to be added very very slowly and you should keep them smaller then 3 inchs. fish this size or larger are going to be packed in there and will not be comfortable. Id stick with small gobies, theres usually a wide range of fish you can have in this group. Id suggest a max of 3 small gobies. This isnt much but your tank will not be able to support much more then that.
Before anything happens to the tank, id suggest doing as much research as your brain can possibly take so you know as much as you can. This will help you at start up and down the road. books are always a good idea.