How do I add labels next to the series on a graph?

Click the background of the graph area. To highlight values on a graph, tick the box next to "Legend labels" in the Chart elements box of Presentation properties tab.

Each label will display the current legend description for each series. If you want to change a label, double-click to edit. You can also edit the default text by clicking on any label and selecting edit default in the Content group of the Presentation properties tab.

For more information, check these materials:

Dynamic Text

Adding x-axis labels