how can i go back and power on my sony x peria c from abd scree notice ????

here i tried to update my phone but lake of self confidence i tried to this option and am in trubble now... what can i do to power on this device.. ??

Welcome to Android Central! More details would be helpful. Did you root the phone and try to install a custom ROM? Or was this an official system update from Sony? What exactly are you seeing now?