Formatting scale bars
A scale is not optional on a geological figure, and a digital outcrop model is no different. A screenshot without one tells the reader nothing about whether they are looking at two metres of section or two hundred.
The scale bar is a display overlay: turn it on from the Home ribbon tab, in the Display group. Its appearance — size, colour, units and how many decimal places the labels carry — is set in the display properties.
Check it before you capture
The scale bar reflects the current view, so confirm it after you have framed the shot rather than before.
See 3D View Display Options for the full set of overlays, and Figures and Images for getting a finished figure out of VRGS.