I'm failing at FreeCAD

The frustrating part, and I do mean frustrating, is that I don't know what I'm not getting... and it is taking way too much of my time. I have a lot to do right now.

To accomplish the Open Source Ecology Developer Test (OSE), I need to be able to put some parts together in a cube, install bolts and draw my initials on a part.

There are a bunch of developer tests there to look at, and I've hunted down a bunch of videos on YouTube. I know that to assemble the parts in FreeCAD that I need to do it in Assembly2. I have tried in vain for hours.

I can get it done in Blender, no problem. I downloaded the parts from the OSE Part Library, opened it in FreeCAD, then converted the file to Stl, which Blender can understand, and built the project in short order.

Rendered (I did forget to put my initials on it).

How do I learn this? Obviously I'm overlooking something basic.