When you need to add an additional data series to an Excel chart you can do so by first selecting the new data. If you included column headings in your data selection when you first created the chart then include the column heading in this selection too. Click Copy on the Home tab, click on the chart and click Paste to add the additional data series to it.
Excel 2007, 2010, 2013 (NOT 2003)
Excel 2007, 2010, 2013 (NOT 2003)
