Fit the front and rear bogies.

Put the rear bogie over the stud. It really is easier if you separate the drawbar. I haven't done that prior to taking this photo - I thought that I could manage without. I was wrong, and it was separated after this photo was taken.

The front bogies are simply rested in place - but there is a tab at the front that needs to be properly located first in a slot at the front end of the chassis .....