Click in the left panel to choose a model universe; the corresponding R(t)/R0 curve will be plotted at right.
To see how and change with time, check the box Plot (m) - () trajectories. Check the Enable Animation box to plot both curves slowly enough to see how the two are related. The dot marking the end of the curve changes from red to blue as it passes through the "present", i.e. the ( ,) point you originally chose. Choose Plot All instead of Plot latest to see all the curves you have generated so far (you can clear the models one by one or all at once with the buttons).