Hi Jimjams!
I had all the same questions a couple month ago. I created a comprehensive Video Tutorial and Blog Post that goes into more detail and explains in 5 Steps how to get the ball rolling when using RTX and DX12 with Unreal & Ray Tracing.
Rendering & Ray Tracing in Real time with Unreal UE4 and RTX Nvidia DX12
I hope that will help you!
Have fun,
cheers! 