Congrats!
16 weeks is a bit early, but some do that.
Open the nests.
Put a fake egg in all but one nest(some don't like the fake eggs).
Hopefully the nests are lower than the roosts,
but make sure they aren't sleeping in nests at night.
It still may take some time for her to find and use the nests, so don't be surprised if she doesn't use them right away.
Redundant maybe, but:
New layers can be quite goofy acting, they don't know what they are doing at first and can be confused and anxious, it can take up to a month or so before they get it all figured out. Putting some fake eggs or golf balls in the nest might help show them where to lay. They may scratch around in the nests for weeks before laying, spreading the bedding everywhere. They will scratch around a bit less in nest as they get used to the routine. Meanwhile, eggs everywhere, some of them can be rather funky looking, soft or thin shelled, huge double yolked eggs.