I think you are referring to this example: https://www.simscale.com/projects/gholami/propeller/
Thus, the coordinates would be (0,0,0). One trick is to go to Simulation Designer > Domain > Geometry Primitive > Point to confirm in the viewer that the coordinate is correct.
As of right now, the easiest way to determine the coodinate is directly in your CAD tool before uploading the model to SimScale. I understand you are doing our meshing tutorial, thus that doesn't apply in this case.