Where do you live and what are your temps like right now. Are they fully feathered. Are you still using the light inside. What kind of coop do you have. Generally speaking. About six weeks of age you can put them in the coop provided it isn't too cold. You could move them to the coop and put a light in there if you have room.
This post will no doubt get relocated to "Raising Baby Chicks" or something like that.
However it depends on when they are fully feathered and how warm your temps are at your location. Generally by 6 weeks old it is ok to get them outside, as long as the nights are not brutally cold still. (20's or below). You can always put a lamp out with them a couple feet above their heads at night only, so that if they do get a bit chilled they can snuggle in for some warmth. If you are having warm days and nights, you can even get them out around 5 1/2 weeks. Good luck and welcome to BYC!