I just noticed that about 30 minutes before you made this thread, you made another one, asking the same exact thing, except you also wanted to add a starfish, and said you had two damsels and one tomato clown, and not five damsels...
You also never said whether or not you have LR, LS, etc. Just that you had a protein skimmer and basic filtration...
So, let's cover things again:
1.) You should not put a starfish in your tank until it has been established for a long period of time. Your LR should be very mature, and you should have a LOT of it, as they graze like cows. If you wanted a sand-sifting starfish, you should have a very mature sand bed and a tank with a larger footprint, so there is more in the way of volume...
2.) Since it appears from your last thread that you already have the Blue Hippo Tang, you should take it back to your LFS. If they won't take it, try another store. If no store will take it, post on here, and I'm sure someone in your area would be happy to take it off your hands. Tangs are very active fish, and like to jet around. They will quickly outgrow a 55 gallon, even a 75 gallon... While some say it's better to put a very small one in a smaller tank, if provided with the right diet and environment, they grow like weeds, and deserve a bigger tank so they can "stretch their muscles."
In the end, I wish you luck on your tank. It sounds like it's a new venture for you, and I can assure you that you've found the right place. Ask lots of questions and do lots of reading
Good luck!