Setup -> Constellations
This brings up a scrolled list of the names and official abbreviations for the 88 constellations. Tap to select the constellations whose figures you want drawn on the sky chart. Turn on all constellations by tapping All; swap the current selections by tapping Toggle. The constellation figures may be drawn in either classic shapes, or as defined by H. A. Rey by setting the check at the bottom.
As a special case, if exactly one constellation is selected when the dialog is closed with Ok, the sky will be zoomed so that one constellation is nicely centered.
Tap X to close the dialog without making any changes; tap OK to install the new settings.