xrandr is your friend. You are going to need to know the official names of the outputs that Linux supports for your hardware, and "xrandr -q" can report those.
Here's an example of a script I wrote that I run when I want to switch to a 3-display configuration (this is very specific to my hardware and display layout, but you should be able to adapt to your situation easily).
xrandr --output eDP1 --primary --crtc 0 --mode 1920x1080
xrandr --output DP1-2 --crtc 2 --right-of eDP1 --mode 2560x1440
xrandr --output DP1-1 --crtc 1 --right-of DP1-2--mode 2560x1440
The reason I don't try to do it all at once, and have the sleeps interspersed, is because my graphics adapter gets confused if I try to configure too many crtcs at once.