Exporting to .stl

[aramsey8]

Please provide some guidance to a first time export effort. I am unclear on how to set the scale so that my desired dimensions are rendered in an stl file. I understand that WU are not set to a particular scale, but have also read that they have a default value. How do I set the scale so that the final product (to be produced on a 3d printer) has the actual size I want. Is there a place where I enter, for example, 1 WU - 1 inch?

I've tried for hours to find the answer online

Sincerely thanks,
Andrew