Welcome to Reef Frontiers!!
What type of lighting does it have? Unless it has Metal Halides or quality T5HO, I wouldn't recommend a clam. Also, an RBTA will typically get too large for a Nano tank.
There's lots of great information on here, to help you with setting up and cycling your tank. Do not cycle with fish. This is very stressful on the fish. Get it set up, with sand and live rock and start testing. You'll want to test for Ammonia, Nitrites and Nitrates. If you use established live rock, and get it in your tank, with little die off, you'll probably not experience a cycle.
If you use rock that hasn't been cured, you'll experience a cycle and see Ammonia climb and peak, nitrites climb and peak, as ammonia drops, and then nitrates climb, as nitrites drop. You want your Ammonia and Nitrites at 0. Nitrates won't drop, without water changes, a protein skimmer or using Macro Algae as a denitrification method. A combination of all 3 is great!!
Also, if you do insist on an RBTA, even though your tank probably won't be appropriate for one, I'd highly suggest waiting at least 6 months, for your tank to stabilize. The clam will also need stable condition, and high intensity lighting.
