Congratulations on your new hens!
They should probably start laying for you at 5-6 months of age. It varies from hen to hen too.
You will need to supply them with oyster shell and layer feed when they start laying. Don't give them the layer feed beforehand because of the extra calcium in it.
Watch out for lice and mites (there is poultry dust you can treat them with at the feed store). Also if they get diarrhea you can check for worms. I am mentioning this since you are getting them when they are grown up a bit. It helps to watch for these things.
They need nestboxes when they start laying, and protection from predators when they sleep (and some keep them in pens during the day, some free range).
They need water and chicken ration (feed), also grit unless they are getting pebbles from the soil. Don't give too many treats (or you will decrease the protein in the total feed too much).
I hope this helps, and welcome to BYC!