I too am new to CAM and CNC. I would like to make a Dust Shoe for my CNC router from Thingiverse STL files. Following is a list of the steps I have taken to get to where I can't create a tool path. Hopefully someone can point out what step/s I've missed or where I am going wrong. I've got this far by searching other posts in this forum and following Youtube videos.
1. Select Model Workspace.
2. Set "Do not capture design history" on recomendation from Youtube tutorial.
3. Insert mesh (stl file) which comes in vertical so I've rotated it 90 deg. and moved it to ground on my XY plane.
4. Scale 25x because the stl file comes in at 1/25th of actual size.
5. Mesh > BRep. Image changes from grey lines and surfaces to black lines with gray surfaces not a solid lookig object.
6. Select CAM Workspace.
7. New Setup.
8. Set Origin to Stock Box Point and select bottom left of top surface.
9. Set Stock to 280mm W x 165mm D x 25mm H.
10. From Tool Library select Metric - Plastic , Pocket, Flat, 6mm diam.
11. Generate Toolpath and get the message "No operation needs to be generated."
Attached is my project as far as I've got and the original stl file.