step 1:

Draw a PCB shape and the main component placed in the PCB. The drawing sheet should be in the top view.

If the drawing sheet is a 3D file, you should transfer it to 2D file as following. You can generate more than one 2D files from different views, and these 2D files overlap if necessary.

step 2:

Export DXF format file from Rhinoceros

step 3:

Import DXF format file to the PCB file of Altium Designer