Let us assume the system is off or running in manual. The display will be similar to one of the images shown below.

To set the system to automatic, press either the up (key 4) or down (key 6) arrow keys.

The display will now look like one of the following images.

Pressing the up (key 4) or down (key 6) arrow keys, will now cycle through the three possible mode settings, Off, Auto, or Manual.

When the display is showing "Auto" as below, press the enter key (key 8).

The display will now look similar to the image below, and the system will be running in automatic.