How to Add a Second Y-Axis on Excel & Make a Second Series at the End of the Chart. Microsoft Excel charts give you a large number of options for displaying the data in your spreadsheet.

To add more data to the Y axis in a line chart, add additional numbers in cells below your existing data. Right-click the chart, choose "Select Data" and highlight all entries in the single column.

In Microsoft Excel, to draw attention to a specific marker in a line chart, drop in a thin line, think of it as a marker.