While it's not necessary to case the kit or use a mint tin for the job, the PCB was designed for such a thing and so we'll cover specifically how to do so.
First, eat all the mints and clean out the tin
The drill guide isnt essential, but it is a little easer than eyeballing it. Note that its pretty hard to get nicely drilled holes in mint tins so perfection may not be attainable.
Drill the two large holes for power and video. Then drill the smaller holes for IR and the LED
Since it's square, you can't drill this hole. Instead use a dremel, dykes or tin snips. Never use your delicate electronics diagonal cutters to cut a steel tin. You will destroy your cutters and fail to cut the tin.
Make sure to place the protective cardboard underneath the kit so that there is no risk of shorting any components against the metal. Check that no leads are too long and could possibly touch the sides.
Use 4-40 screws and hex-nuts to attach the kit to the case. You're done!