13. Right-click the Horizontal (Category) Axis and then, on the shortcut menu, click Format Axis.
14. In the Format Axis pane, with Axis Options selected, set the Axis Position to On tick mark.
15. Next, under Tick Marks set Major type to Outside.
16. Then, under Labels, set the Interval between labels to Specify interval unit and set to 2.
17. Next, click on the Fill & Line icon and, under Line, set the Solid line Color to Black and its Width to 0.25pt. The chart should look like this: