To have it conform you need to create the model in such a way that when its OBJ is imported into Poser it will correctly align to the figure when it is at its zero pose/zero translation. In this instance the table would have to be modeled upright not laying flat. Next I suggest that you name the bed group "hip" and set its joint center to match the center point of Judy's hip.

As for a conforming tutorial, click on the link above. There are many there. Details of my one are on my site.