Select a series (one single click) or a point (two single clicks), select
the first item on the Format menu (or press CTRL+1), and on the data labels
tab, select one of the options for a data label. If you want a custom label,
choose any default, then select the data label and edit its text.
To add a number of labels based on cells, try one of these free and easy to
use Excel add-ins:
