Creating a 3D Solid for Modeling Stresses due to Centrifugal Forces

Hi Everyone,

I obtained a model of a bladed turbine disk from GrabCAD. I am trying to model the von mises stresses due to rotating at 1074 rads/sec. I am new to LS-Dyna and I am struggling creating a solid mesh. Below is a screenshot of what I am getting. To be clear I can create a shell mesh but I need a solid mesh for this analysis. I tried tetrahedral meshing but I can't select anything for some reason. Please let me know how to select surfaces so I can make a solid mesh. 

Thanks.