HELP I have 2 horses that haven't been Stalled in many years How do I get started

I adopted two horses, one of them was stalled but has not been stalled in over 3 years and the other horse was never stalled. Due to medical condition ( Scratches) I have to remove them from the pasture at night, but not sure how to get started, do I just put them in the stalls and just watch them, or is there another less stressfull way of handling it. Please Help me.

How were they in the trailer upon delivery??
If they were fine in there then they shoud be fine in the stall

Most horses are fine about it. If they were happily stabled a few years ago, they should be ok now as long as they are within sight of each other or other horses.
Just make sure they have sufficient hay to munch on through the night, and they'll be fine ;)

A lot of horses should be fine with the whole ordeal. If they were fine with it then, they should be fine with it now. I would stall them, but for the first while, keep a good eye on them. If they're good for a day, they'll be fine for the night. Just keep a steady eye on them.

Stock em up on hay and water and they wont miss the outside.

I agree, as long as they have enough hay, fresh water and a regularly cleaned, comfy stall - they should be fine.

Being able to physically see other horses, would also be very calming for them.