Excel 2013 lets you add various elements to any graph including axes titles, chart titles, and data labels, using the Add Elements button. To see how this is done, let’s assume we have a graph like the one below.
When you select the graph by clicking on it, you will see three buttons appear in the upper right corner of the graph. The button with the plus is the Chart Elements button. This button allows you to format how the graph appears in the worksheet.
For instance, if we check Axes Titles we can add labels to each axes. Notice that a panel also appears along the right side of the page that allows you to manipulate how the axes titles appear in the graph. By highlighting the text in the titles, we can modify the text to reflect appropriate titles for the graph.
After these modifications, you might see a new graph like the one below.