It was pretty straight forward, just instead of using:
data.addSeries(xs, ys);
I had to be using:
LineChartSeries chartSeries = data.addSeries(xs, ys);
chartSeries.setTitle("My Title");
Didn’t look at the API that using data.addSeries(xs, ys);
returns a single LineChartSeries
object onto which I can set a title.