You use the button with the <> arrows to move through the menu selections. Use the menu key to select the function you want to change.
Below is an excerpt from the Acer manual. The manual can be found at http://www.retrevo.com/support/Acer-X203H-Monitors-manual/id/23224bh549/t/2/
Front Panel Controls
To turn ON or OFF the power.
Lights up to indicate the power is turned ON.
3.Empowering / Exit:
1) When OSD menu is in active status, this button will act as EXIT-KEY(EXIT
2) When OSD menu is in off status, press this button to select scenario
4.Auto Adjust button / Exit:
1)When OSD menu is in active status, this button will act as EXIT-KEY (EXIT
2)When OSD menu is in off status, press this button for 2 seconds to
activate the AutoAdjustment function.The Auto Adjustment function is
used to set the HPos, VPos, Clock and Focus.
5.< / >
Press < or > to select the desired function.Press < or > to change the
settings of the current function.
6.MENU / ENTER:
Activate OSD menu when OSD is OFF or activate/de-activate adjustment
function when OSD is ON.