Here's how to do it:
- Click on the chart.
- In the upper-right corner of the chart, click the Chart Elements button (a plus sign icon).
- Check the Axis Titles box.
- Click the axis title placeholders and enter text like "Sales" for Y-axis and "Months" for X-axis.
- Select the axis titles and use the Home tab to adjust font size, style, and color as needed.