Assembly is pretty straightforward, here's what you need:

1x Top cover (print)

1x Bottom cover (print)

3x Button (print)

4x M3x10 bolt (you can optionally use M3x12 or 15)

Allen key

Place the PCB inside, push through bolts and screw the top. You may need to hold the case firmly to screw it together ideally, tolerances are tight so that there's enough space for the thread to go through.

Disclaimer: tolerances are mostly 0.4, so count that in if you are printing it, I advise you to print optional tolerance test to see if it's okey for you and possibly scale up the model (max. 5%).