First, disconnect any additional devices that may have caused the breaker to overload and trip. In order to reset a breaker in your electrical panel, you must push the breaker firmly to the off position which then resets it, then you must firmly push it back to the on position. Some do not push the breaker hard enough past the off position, which can cause the power to remain out. Remember, this is a mechanical device, so this may require several attempts. If you think that you have reset the breaker correctly and still have no power, this could mean a serious problem. Call an electrician immediately.