Enabling data label modification options involves alternate steps depending on whether you want to modify some or all data labels. To change all data labels, click anywhere in the chart.

Type in the interval that you want to use for the X-axis labels. The first axis label displays, then Excel skips labels until the number of your interval, and continues on in this pattern.

Learn how to change, edit or rename a Data Series name in Microsoft Excel Graph or Chart without editing the original row or column name.