Please note: you cannot change the title of the chart that you have already saved as a PDF file on your computer. You need to create a new chart and add the title you want while generating it.
If you create a chart on your family site online:
Once you have selected the chart type and style, scroll down the chart wizard to the third step.
There you will see the option to edit the title of the chart, which is generated automatically when you select the type of the chart.
If you create a chart using Family Tree Builder software:
Once you have generated a chart, click on the ‘Options’ button above the chart display in Family Tree Builder to change the chart title: