For the time being the 3D models only really work well on a PC.
My sincerest apologies to those Apple folks out there but Autodesk doesn’t seem think it should be easy for you and seems to offer nothing but vaporware. There are options but they all seem to be complicated, expensive, or sketchy. If you can find a reasonable solution for viewing *.dwfx files on an Apple product please let us know so we can share the joy.
If you are on a PC…Depending on your browser you may need to install Autodesks Browser Add In or in the worst case download Autodesk’s free Design Review software.