Based on the Sydney General Post Office.
Firstly, there are alternate versions of the first floor pieces (named with _alt), which have a larger door if it fits better with your scale.
Print 4 of each of all the files (8 pieces per floor). It's a big print! You can print more of Level02 if you would like more intermediary levels; my print (shown in the photos) has two floors of the same pieces, and you could print more if you desire.
Once printed, the pieces all come together with dove tails, and each floor is notched into the one below so you can take it apart if necessary. It may take some forcing to make the dovetails fit. The roof sides fit into the notches of the upper floor, and the flat roof pieces slide down into the grooves.
Use glue if you feel you need it, but my print did not.