This screen shows the result of clicking on the fx icon and then selecting the function AVERAGE from the list of available functions on the left. Notice the plain "=" in the formula box. That means we have not yet actually put in the function. Also notice that the box labled "Next >>" has a light orange border which indicated that clicking it is our next step.
Click on the "Next >>" icon to actually insert the function AVERAGE into the Formula box and then go to the next screen to see the result.