08-12-2013 01:49 PM
You should be able to find it here: http://www.usa.canon.com/cusa/consumer/products/cameras/slr_cameras/eos_m_ef_m_22mm_stm_kit#DriversA...
Pick your OS type and version. That will expose options for software, drivers, etc. but one of the categories is "Firmware".
Download and extract the zip file (or open the .dmg file if you're on a Mac). The instructions to install the firmware are included inside that zip file.