Micromax phones use SP Flash Tool to update the firmware but this involves in dealing with custom ROMS, drivers, etc. It's a very risky process because there is a big possibility to brick the phone to make it completely unusable. To avoid this issue, use the official OTA updates available from within the phone. To access the update page go to Menu > Settings > About phone > Software update. Register if necessary, connect to a WiFi network and then check for firmware update. If there is any you can apply it right away. To avoid other problems, make sure the phone is properly charged to 85 % or more.