Ok so you should have 4 things for your chickens available pretty much all day every day.
1. fresh water
2. complete chicken feed (whatever grower or all flock you can get at your store)
3. grit in a separate bowl on the side (depending on your soil they may just eat small rocks off the ground and be fine, but sometimes the soil doesn't have enough of the right size rocks for them so I'd buy a small bag of grit at the feed store to be safe)
4. oyster shell in s separate bowl on the side (once they get laying or start laying any females will pick at this as needed, some need more calcium than the feed provides in order to make good strong shells)
Here is also a link to the chicken treat chart; there are loads of healthy snacks you can feed them if you have them available.
https://www.backyardchickens.com/articles/chicken-treat-chart—the-best-treats-for-backyard-chickens.47738/