Gather the 2 end walls and door frames.

Glue the door frames onto the outlines on the end walls.

Glue the end walls into the base

Peel the protective film off the back of the clear flexible roof

Slot and superglue  the clear flexible roof into the holes along one edge with the engraved detail facing out

Put super glue on the top of the end walls and along the row of slots on the opposite side.  Bend the roof over the walls and slot it in place.

You are finished.  Prime with Rust-o-leum Profesional Enamel flat black and paint as normal with hobby paints.