You usually set this in your X server's configuration file. Open /etc/X11/xorg.conf and look for lines like
Code:
Subsection "Display"
Depth 8
Modes "800x600" "640x480"
ViewPort 0 0
EndSubsection
and change them to look like this.
Code:
Subsection "Display"
Depth 8
Modes "1024x768" "800x600" "640x480"
ViewPort 0 0
EndSubsection
You can add any resolution your lcd can actually display in front of the "Modes". There are three sections of this for different color depths, add the wanted resolutions all of them. Then restart your X server for the changes to take effect.