One word, S C R A T C H. We have small plastic cup, holds maybe 6 Oz of scratch when filled to the top. We fill it about 2/3 of the way in the evening just before dark. I will shake it and then throw out some scratch. While they are scratching and pecking I set up a chair and sit with them. Chickens are naturally curious so they will investigate you. And every evening they will get closer. In about a week they will calmly hang out with you. After about 2 to 3 weeks of the scratch can shake they will come running and noisily file into the coop at night. Or simply run up to you to see what you have during the day.
You don't have to give the treat every time but if you make it part of the evening lock up routine, you can use it to get them in early, if you want to do something before dark and you let them out.