Yes, there are several ways of converting an imported mesh into a body that can be used in the CAM workspace. However it's always much better to work directly with CAD file formats, such as Fusion's native .f3d, or .step, .sldprt etc.
http://forums.autodesk.com/t5/design-and-documentation/foot-insole-modelling/td-p/5715117
If you have any more questions let us know!
Jesse
I would definitely use the STEP file format (*.stp) if you can get that to work. STL was never intended as a data exchange format and includes only heavily triangulated mesh data. STEP on the other hand is solid model data.