Instructions
Press "Esc" while in the game to view the main menu. Click "Options." If you are not logged into the game, click "Options" at the login screen.
Click the "Resolution" box at the top. A list of available resolutions will appear.
Click one of the "Wide" resolutions. Click "OK." If your monitor supports the resolution, your screen will appear black for a moment, and the game will quickly return stretched across the screen. If your monitor does not support the resolution, your screen will remain black for a few seconds, before reverting back to the previous resolution. If that occurs, choose a lower resolution.