Help!! How to install an outside nest box - no need to respond!!!

I haven't seen anywhere how the outside nest boxes are installed. I am a newbie and presently building my first coop.
I am building a playhouse coop without plans for 4 chickies. Plan on making one nest box, 1/2 plywood to divide it into two
24 1/2 x 12 x 16, is this a good size? How do I install it on the side of the coop?

Thank you in advance!!

I googled and found great instructions with pictures - there is no option to delete that's why this post is still here.