Displays

See Shortcuts for keyboard commands…

This page from the GNOME Display Manager Reference Manual might prove useful if you want to make the changes permanent.

Multi-Monitor

From Change primary monitor in Gnome 3

Primary

If the laptop screen is blank and you want to make your monitor the primary display, then list your displays:

$ xrandr
Screen 0: minimum 320 x 200, current 3280 x 1080, maximum 32767 x 32767
LVDS1 connected primary 1360x768+0+312
   1366x768       60.0 +
   1360x768       59.8*    60.0
   1024x768       60.0
   800x600        60.3     56.2
   640x480        59.9
HDMI1 connected 1920x1080+1360+0
   1920x1080      60.0*m
   ...

In this example, I wanted to set HDMI1 to be my primary display:

xrandr --output HDMI1 --primary

Resolution

From How change display resolution settings using xrandr

To change the resolution (mode) on a monitor…

List the displays using xrandr (see example above).

Then set the output for the screen e.g:

xrandr --output LVDS1 --mode 1360x768