In Lubuntu, multi monitor display settings are not enabled by default. So when you attach another monitor with your laptop for presentation or extended display, nothing will happen. You can take care of that using Monitor Settings, but it does not allow you to layout the displays. Arandr is a simple visual tool to change the relative position of your displays.
To install it, you will have to open Lubuntu Software Center, and search for Arandr. Simply add it to Apps Basket, and then install it from basket.
Activating Another Display
To use it, you will have to got to Lubuntu Menu, then go to Preferences. Click on Arandr. You will have to ensure that you have started it after plugging in another display, otherwise it will not be able to detect the new display. On Arandr, by default one rectangle will be there which represents your current display.
Click on Outputs menu. Of the available options, one will have the option to be activated.
Configuring Another Display
After activating the second display, by default it will mirror your primary display.
To make it extended, simply drag the second rectangle to the side of primary display. It is dragged right to primary display, meaning the display has been extended to the right side.
Click on Layout Menu, and click on Apply, or just press Ctrl + Return to apply your new display layout settings.
On some laptops there will be more than one external monitor port, in which case you may have to turn off the unused port before activating the desired.