You can edit and modify all the parameters related to a chart by entering the Edit mode. Doing this basically turns Calc into StarOffice Chart (while you are editing the chart). StarOffice Chart's Main toolbar will appear at the left side of the workspace and the menu bar will contain commands related to StarOffice Chart.
To enter the Edit mode, select the chart and then right-click on the chart. Select Edit from the context menu. Or, you can just double-click on the unselected chart.
Figure 10.12 shows a chart that is in Edit mode. You will find that most of the commands that you need related to editing or modifying the chart are contained on StarOffice Chart's Main toolbar.