Click on the "Chart Design Mode" button in the right-hand corner of the chart.
This will then open column selection. Each column is pre-selected and added to the chart.
A column/ series can be removed from a chart by simply toggling it off. Once the toggle is greyed out the series will no longer show on the chart.
Once you have removed all of the columns you no longer want to appear in the chart, you click the "Save Chart Design".
Similarly, if you want to discard the changes you have made, click the "Discard Changes" button. This will exit Chart Design Mode and return to the chart view.