There are three hinges that use a piece of 1.75mm filament. First connect the piece with the nozzle slots to the inside of the top piece. the slots should face the top.

 Then snap the piece with the slots down into the bottom piece, sliding the conical parts into the matching slots.

After that, close the box and connect the back hinge. 

It may be a good Idea to run the strand of filament through each hinge piece a couple of times before trying to connect them, as they are intentionally a tight fit.