Chickens!

Hi! I'm new to having these birds as pets- I've been given one as a gift that is approx. 3-4 weeks old. It's in a spacious box lined with newspaper and hay, and has access to clean water and bread (buying seeds now).
I know i should also prepare a cage for it, and i've got one im disinfecting. What I would like to know is if there are any special needs that chickens have, i.e special food, access to grass, grit, etc.

Thanx!