Hens not interested in nesting box

[bmartin85]

I have had 3 girls for about a week and as they explore the coop I haven't seen any of them getting remotely close to the nesting box, I understand they are not laying yet but I am worried they will lay in the yard instead of the boxes

 

[Ol Grey Mare]

I have had 3 girls for about a week and as they explore the coop I haven't seen any of them getting remotely close to the nesting box, I understand they are not laying yet but I am worried they will lay in the yard instead of the boxes

They may well lay in the yard even if they were showing interest in the nesting box - but that is okay, as it is something that can easily be addressed if/when that time comes. If they aren't actively laying yet, you really don't want/need them to be interested in those boxes as the only thing they'll leave in them at this point is poop, and you don't want poopy nest boxes.
How old are these girls and what breed are they?
As they start to show signs of approaching the onset of production, that is the time to place some "bait" (golf balls, wooden eggs, etc.) in the nest boxes to give them the idea of what those boxes are meant for - and to start watching for them to show interest in the boxes. The first eggs are a learning experience for them and they don't always have the most controlled experience in laying, which leads to the eggs ending up in places other than the nest box - not the end of the world as with time and practice they get the idea.
By "in the yard" - are they free range in an open yard or are you referring to an enclosed run as their yard? If it's the former, you can assist the box training by confining them to the coop/run for a while when they start to lay so that the best option available to them is the nest boxes you want them to use

 

[bmartin85]

They are around 19 weeks old, I have 2 barnevelders and 1 Silver laced wyandotte, they have a coop with a yard attached