Hi and welcome! Is there water in the 55? If not, you need to start your tank by putting in sand, rock (live or dry), and salt water made with RO/DI water. Then you also need test kits at LEAST for Ammonia, Nitrite, and Nitrate. You should also get Phosphate, Alkalinity, Calcium, and Magnesium especially if you plan on keeping a reef tank. Then cycle your tank without fish preferably. You can use microbacter and a bit of fish food to start the cycle. Ammonia will rise, then nitrite, then nitrate. You can start slowly adding livestock when your ammonia and nitrite are zero and your nitrate is either zero or fairly low.