How do I add value labels to the x-axis?

Click on the background of the graph area and open the presentation properties tab at the top of the window. In the elements group, tick the box “vertical axis value labels.” If you have vertical lines in your chart, their x-values will now be displayed.

The labels will by default show the last valid value. To change this, double-click on the label and change the text to your liking.

For more information:

Dynamic Text

Adding legend labels on a chart