Help with pet chickens?

I wake up today to see 3 young chickens in my garage. They seem very tame, letting me and my younger brother carry and pet them. We moved them to our backyard with some gravel and grass. I need help on what I can feed them. I gave them some guinea pig food today. Also, where to house them(there's one stray cat and I don't want them to get eaten.). Any other information would be really helpful! Thanks! Also, could I give them a bath?