Attached Link: http://www.angelfire.com/art2/cheapskate/3dsimport.html

The linked tutorial applies especially to imported 3DS meshes, but the principles are the same for all. The warning about spaces is worth noting, too. If you made the prop yourself in OBJ format, UVmapper can be used to re-assign the materials; then just import into Poser and set them up, and save to the library. A third party prop is easier to hack with the text editor method.