whitetailwood2015:
To load the STL file into VCarve, you use the Model --> Import Component / 3D Model command, from the main menu. If you prefer the icons, look way down at the bottom of the drawing tool panel (on the left, typically). At the very bottom, see those tabs? Click on the Modeling tab, and the tool icons at the top should help you get those models in.
One thing to note: in some cases getting Vectric to cut the top/bottom of a 3D model can be confusing, as the controls seemed (to me), very counterintuitive and/or bordering on nonsensical.

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Hope that helps,
Thom