Dan, Here are two photos. 1. Shows the armature and the side that joins it with the electrical connections. 2. The same of the armature but the other of brush and spring cavities.
From these two photos, I would place the brushes into the two indents provided for them , then I would lower the other half of the motor onto it.
I'm not sure if the two plates covering the outside of the brush holes are the actual springs that apply pressure to the brushes, and keep them against the armature.
If in fact there are two springs that go behind the brushes, I would place the springs and brushes into the frame, then place a business card over them to hold them in place. You will have to cut a slot in the card to allow the card to be slid out, once the armature shaft enters the bearing once I had the other half of the motor in place, Carefully slide the business card out, all the while keeping slight pressure on the armature half so nothing falls out of place.