Instructions
Open "StarCraft II: Wings of Liberty." Type your username and password to log in. You cannot play the game without an active Battle.net account.
Click "Options," which is located in the lower-right corner of the screen.
Select the "Graphics" tab on the left side of the "Options" menu.
Click the drop-down arrow next to "Resolution." Select a larger resolution than the one you're currently using. It may take some adjusting to find one that is large enough to suit your needs and still looks appropriate on your monitor.
Click "Accept" to apply the changes to your game.