Press the "On" key (row 10, column 1 on the TI-83 keypad) to turn your calculator on.
Press and release the "2nd" key(row 2, column 1, often a yellow-orange color) and then press and release the "down arrow" key (row 3, between the fourth and fifth column, with a white arrow pointing down) to lighten the screen. Observe the number in the upper right hand corner of the screen decreases by one for each press of the "down arrow" key. Press the "down arrow" key again to lighten the screen to the next brightness level.
Press and release the "2nd" key(row 2, column 1, often a yellow-orange color) and then press and release the "up arrow" key (between the second and third rows, between the fourth and fifth columns, with a white arrow pointing up) to darken the screen. Observe the number in the upper right hand corner of the screen increases in value by one. Press the "up arrow" key again to darken the screen to the next brightness level.
Press the "up arrow" key continually until your reach the lowest brightness level (9). Press the "down arrow" key continually until you reach the highest brightness level(0). Use the "up arrow" key and the "down arrow" key to set the brightness level that you find provides the right level of brightness for your work.