Noise and Idle

We just replaced my engine, and now when we start it, it idles between 1000-2000 rpm and it makes a loud noise. We are not sure of what the noise is and it is frustrating? If you have any ideas, please let me know.
Thanks!!!

Where does the noise sound like it is coming from? ie. Top(Head), Bottom (transmission area, etc.)., Belt side(A/C, altenator, etc.)

What kind of noise is it? Tapping, clunk, whine, etc.

What engine is it? (1.8, 1.9, etc.)