Left; Right - Sony VAIO VAIO PCG505F User Manual

Slide the LCD lock lever in the direction of the arrow, and lift the
cover.
Slide the power switch on the right side toward the front of the
computer until the green power indicator light turns on.
If necessary, adjust the brightness controls for the LCD display. To
decrease the brightness, press Fn+F5 and then the down or left arrow
key. To increase the brightness, press Fn+F5 and then the up or right
arrow key.