When you create a chart, the legend appears by default, but you can hide the legend or change its location after you create the chart.
You can also show a data table for a line chart, area chart, column chart, or bar chart. A data table displays the values that are presented in the chart in a grid at the bottom of the chart. A data table can also include the legend keys.
Show a chart legend
-
Select a chart and then select the plus sign.
-
Select Legend and select the arrow next to it.
-
Choose where you want the legend to appear in your chart.
-
Select Secondary Axis for the data series you want to show.
-
Select the drop-down arrow and choose Line.
-
Select OK.
Hide a chart legend
-
Select a legend to hide.
-
Press Delete.
Source: Microsoft