Monitor Won't Properly Display
If your monitor is not displaying at all, first ensure the computer is turned on. Also check that both the HDMI cable running from the computer to the monitor is securely plugged into both, and that the monitor's power cable is also plugged in. Most monitors have a power button on the bottom or back, turn this on if it is not already.
If your monitor is displaying a screen, but not the screen you want it to display, open "Settings" -> "Display" and select "Extend these displays" from the dropdown. You can rearrange the displays by clicking and dragging them if they are in an improper order.