How can I add a title to a graph?

In every graph, there are five standard graph title positions: Title and Subtitle (both at the top of graph), Left, Right, and Footnote. They can be edited in the Graph Titles/Text dialog, accessible by double-clicking on a specific title.

The titles can also be edited in the Graph Titles/Text options pane of the Graph Options dialog [accessible by clicking Graph Options on the Format tab (ribbon bar) or by selecting Graph Options from the Format menu (classic menus)].