Hello I have a footprint and a stackup shown bellow.I imported a step file .
In the manual they say that i need to select mechanical layer 1 to place the STEP file on the footprint.
I cant see in the stackup bellow this layer.
also i dont understand the logic of why we place the component of the resistor on the mechanical layer1?

 

Yes, select Mechanical Layer 1 (or any other Mechanical Layer) for placing the STEP file for the component.
What you are doing is placing a physical representation of the component onto the footprint.