Buttons:

-Backlight Control button (located at the top of the display).

-Alert Set button.

-Down Arrow button for setting preferences in SET MODE and viewing historical records.

-SET button to enter SET MODE.

-Up Arrow button for setting preferences in SET MODE and toggling between Indoor readings or heat index and dew point.

-Mute alarms or lightning detection.

ABC Switch - Located in the battery compartment.

Reset Button - Located in the battery compartment. Press and hold to reset the display back to factory defaults.

Wind Chill - Appears at the top of the display to the left of RAIN when the temperature is =/< 32ºF (0ºC) and the wind speed is =/>1mph.

Potential Ice Warning Icon - “ICE” appears at the top of the display to the right of OUTDOOR when outdoor temperature is =/< 39ºF (4ºC).

Set the Time, Date & Units:

Press the button, located on the front of the display unit, to enter SET MODE. Once in set mode, the preference you are currently setting will blink on the display.
To adjust the currently selected (flashing) item, press and release the or arrow buttons (press and HOLD to fast adjust).
To save your adjustments, press and release the button again to adjust the next preference. 
The preference set order is as follows:

AUTO DST ON/OFF
12/24 HR
CLOCK HOUR
CLOCK MINUTE
CALENDAR MONTH
CALENDAR DATE
CALENDAR YEAR
TEMPERATURE UNITS (ºF or ºC)
You will automatically exit SET MODE if no buttons are pressed for 10 seconds. Enter SET MODE at any time by pressing the button.

Display Backlight Settings:

This display unit features three brightness settings (High, Medium, and Low) and an Auto Dim mode. Brightness is at its highest setting by default. Pressing the button once dims it to the Medium setting. Press the button again for the Low setting. Pressing the button a third time will activate the Auto Dim mode. When in Auto Dim mode the display automatically dims to its lowest brightness setting at night and brightens to its highest setting during the day. When in Auto Dim mode a light bulb icon will appear on the display next to the time.
Press and hold the button for 5 seconds to disable the backlight. Once any button is pressed, the backlight will return to your selected setting.

Learning Mode:

Self-Calibrating Forecasting uses a unique algorithm to analyze changes in pressure over a time period (called Learning Mode) to determine your altitude.
After 14 days, the Learning Mode icon disappears from the display screen. At this point, the self-calibrated pressure is tuned in to your location, and the unit is ready for superior weather prediction.

Weather Forecast:

AcuRite’s patented Self-Calibrating Forecasting provides your personal forecast of weather conditions for the next 12 to 24 hours by collecting data from the sensor in your backyard. It generates a forecast with pinpoint accuracy - personalized for your exact location.

Barometric Pressure:

Subtle variations in barometric pressure greatly affect the weather. This weather center displays the current pressure with an arrow icon to indicate the direction the pressure is trending (FALLING, STEADY, or RISING).

Outdoor Historical Records:

Press  (Down) to view each outdoor historical record. Records that are available appear in the following order:

48 hr Rainfall
Week Rainfall
Month Rainfall
Year Rainfall
Max Wind Speed recorded in the last 60 minutes
High Temperature recorded since midnight
Low Temperature recorded since midnight
High Humidity recorded since midnight
Low Humidity recorded since midnight

Programmable Alarms:

To enter ALARM SET MODE, press and release the ALERTS button. 

To adjust the values for which the alarm will sound, press and release the SET button on the desired value; it will start flashing. Next, use the or arrow buttons to adjust the value. Then press the SET button to save your selection. 

To enable/disable the alarm for the currently selected item, press and release the or arrow buttons. A icon indicates that the alarm is enabled. The alarm disabled icon looks like this . 

The preference set order is as follows:

Outdoor Temperature
Outdoor Humidity
Wind Speed
Rainfall

Wi-Fi Setup:

AcuRite® Optimus Weather Station Wi-Fi Setup

Disable Wi-Fi Feature:

To disable the Wi-Fi feature, press and hold the and arrow buttons for 10 seconds. Use an arrow button to toggle to OFF and press the button to confirm. The Wi-Fi icon next to the Optimus sensor icon will disappear, and you will not be able to set up the Wi-Fi feature.

Calibration:

AcuRite® Optimus Rain Calibration

To calibrate the outdoor temperature, press AND HOLD the , , and buttons at the same time for 10 seconds. 
Note: all display data is hidden except for the value being calibrated. A (wrench icon) will appear next to the value being calibrated.

Press the or buttons to calibrate the data value higher or lower from the actual reading.

 Press the button to confirm the calibration adjustment. 
Note: The (wrench icon) remains illuminated next to the calibrated value.