Wow! I can't believe they were inside for a whole year! Usually by the time they're feathered out, as long as the weather is warm, they start going outside at least for the afternoons. Our 8-week-olds are already big to be indoors, but the evenings have been cool and we need to add an extra roost to the coop so they're room for them with the year-olds.
Were they closed in this coop the whole time? Or did you have a big space inside for them? Or did you get them from somewhere else? They're probably a little afraid of the wide open space. Our chicks always are the first couple times they're out.
Our year-olds have been in the coop since they were about 3.5 months old. They have the coop with an enclosed (hardware cloth/chicken wire) run so they come in and out from early morning to evening. When we can be outside, they also get to free range in our unfenced
Do they have an enclosed outside run? Or is it just the coop in an unfenced yard? If you can do even a simple run (2x4s or PVC covered in hardware cloth or small chicken wire), it will give them a safe outside space.
Obviously it's unusual to hear of chickens a full year old who've never been out. As suggested above, I'd carry them out and put them in the grass. They may take a while to get used to it. But they need to scratch and explore!
Let us know how it goes getting them used to it.