You may already know this, but a tank is the most difficult tank to run in the entire hobby (except for, perhaps, a 5 gallon system). Such small systems are inherently unstable, and when there is a problem, it becomes a major problem quickly, so you will need to stay on top of the tank's conditions continuously. To get started, fill the tank with freshly made salt water (RODI-based, please), set up your sand and rock, and then place a cocktail shrimp into a nylon stocking and add it to the tank. When the ammonium levels reach 1.0 remove the remnants of the shrimp and continue to follow conditions as the nitrites rise, then fall, and the nitrates then rise. At this point you can do a water change (or a series of changes) to bring the nitrate levels down. At this point you can add one fish. I would counsel against a damsel - they become very aggressive and may even attack you. Worse yet, they are generally impossible to remove, so you will be stuck. You could add a clown at this point, then wait about a year before adding an anemone. The anemone needs consistently high quality water conditions, a situation you won't achieve until the tank matures. While you are waiting you could add some clean-up inverts, including snails, hermits, etc. Remember - for the anemone you are going to need intense lighting, T5, halide or LED, a skimmer and/or a refugium with macroalgae in it.
