1. Touch the Flash (Auto) icon.
2. Select the desire option.
a. Flash Auto - auto flash when needed.
b. Flash ON - Flash always ON.
You can also refer the page # 12 and 23 of 108 in Instruction Manual of the Camera for detail
information to turn on the Flash.
To download Instruction Manual check the link given below:
http://esupport.sony.com/US/perl/model-documents.pl?mdl=DSCT77NOTE: You can not use the Flash when the Camera is set to Burst or Multi Burst mode. You can not use the Flash when the ISO or Twilight mode is selected in the Scene Selection. You can not use the Flash when mode dial is set to Movie also.
Good Luck!!!!!!!!!!!!!!!!!!!