As much as Community Cycles would love to be open 24/7, we need time away from our Shop. Mostly to ride bikes.
When we are closed and you just have to make a repair to keep you riding, we recommend the following videos from Park Tools to help you keep riding. Also check out all the other Park Tools bicycle repair videos for other more complex repairs or maintenance.
How to Adjust a Rear Derailleur
How to remove and install a bicycle tube and tire
How to remove and replace a wheel
How to remove and install pedals