If you want to change your screen resolution, while still running Linux but you are not using Gnome or KDE, which gives good options to change screen resolution, you will have to use the xrandr command
If you enter it alone:
xrandr
It will display the list of available reolutions.
Now to change from one resolution to the other just enter and xrandr and the resolution with the -s option, like this example:
xrandr -s 1024×768
and it will change your resolution to 1024×768 (obviously) 
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