Found first egg in outside run in sandy area, nest box help.

It was so awsome to get the first egg tuesday , came home from golf about seven and went to give my girls a treat , sat down in my chicken chair, looked to the side with one on my shoulder. And low and behold there in the run was a perfect tiny egg laying in the chickens beach sand. My Question is how to get them to lay in the boxes I have no adults to give example to the pullets these are my first chickens and they spend alot of time rangin in the yard and i dont want to be finding eggs all over the yard and none in the boxes that i made lol . should i leave them in the run till i start getting eggs in the boxes or keep letting them roam the yard?I have some that are 18 weeks, and some that are 16 weeks. also one of my 18 week olds is a roo and he is going after the hens full bore but they dont seam to want anything to do with him it is so funny to watch him chasing the hens all over the yard wings flappin and head down full out run , I have seen him catch them a few times and mount them but only hangs on for a few sec.is that normal im sure he cant get anything acomplished in that short of time? will the hens become more submisive as they get older? I have golf ball in the nests now any ideas about getting them to lay in boxes would be awsome thanks.