Click and select the Font Preferences tab.
The Chart & Legend section shows the font type currently used on the graph and the legend, the legend font size (in points), and the graph font size (Small, Medium, Large).
To change the size of the font on the graph, select one of the Chart Font Size radio buttons (Small, Medium, Large).
To change the Legend font size, click the Change button. (You can also change the Graph and Legend font type.)
Click OK to close the dialog and save your changes or click the Apply button to test your selections without saving your changes.
For more information about the fields in the Font dialog, refer to the context-sensitive help.