How to: Add a legend to an Excel chart.
Solution:
Select the chart, select 'Insert' menu and select 'Legend'.
To add a legend:
1) Double-click on the chart to add a legend. (A striped border with handles appears around the chart.)
NOTE: If the chart is on a separate chart sheet in Excel, click the tab for the chart sheet. (A striped border with handles appears around the chart.)
2) Select 'Insert' menu and select 'Legend'. (Excel inserts the legend on the chart and resizes the chart to accommodate the legend.)
3) (Optional) Resize the chart or adjust the size or the location of the legend.