Good luck with your poultry raising adventures, and I hope you find everything you need to know. Don't forget to take a look at BYC's very useful learning center (If you haven't already)! The learning center as well as the forum should answer your questions! There is always something new to learn! Glad to have you here! See you around with the flock. It should at least be 8 weeks old. It depends on what your weather is like.
Yes, it depends on your weather and climate conditions right now. But generally you should wait until they are at least 5 or 5 1/2 weeks old and fully feathered. By 6 weeks they can definitely handle going out to the coop. When you do take them out to the coop, if your night time temps are still cool or cold, take the heat lamp out with the birds. Use it only at night. You don't have to have it right down on them, but close enough to take the chill off of them. They can all snuggle up and stay warm. Only use it at night and you can take it away after about a week. Then they are good to go! (Make sure to permanently attach the heat lamp so it can't fall and start a fire. Never rely on the clamp when you can not supervise).
Good luck with your new babies! If you have any questions, that is what we are here for. Welcome to BYC!
It also depends on how many you have. They will keep each other warm. I moved mine out at 4 weeks once they were feathered. Kept them confined to the coop with a heat lamp for the first week. After that they were free to go and come to the run during the day. We still have cold nights here in RI (30s) and they all are doing fine.