If using base rock only (BR), you will need to cycle it with the tank (so the cycle process would apply).
If you are adding BR to an already established tank, you can just drop it in...BUT, if there are dead critters in the BR, they will decompose. My suggestion would be to put any BR in a bucket of SW
, with a heater and ph, wait for 3-4 days and test for ammonia. If no ammonia is present, you should be able to safely add it to you tank...