The screenshot below shows the above twilight scene as captured by the app.
To measure the rising moon's altitude above the horizon, first pan and zoom (drag and pinch gestures) to center the cursor over the moon. The slider top left controls the cursor diameter. Once aligned, press the 'pin' button bottom right.

Now hit the button top left (⟂) to  toggle a horizon line reference. Pan and rotate this reference line to match the horizon of the photo. We don't have an open sea horizon in this example, but the shoreline of the farther island to the right will do fine as a so-called 'horizon short'.

That's it for the altitude measurement. To do the sight reduction calculation and and plot the resulting line of position, hit the sextant icon button to export the measured altitude to Celestial Navigation 360. The latter opens directly in a New Sight wizard for the date/time and altitude it has received.

Don't forget to set Dip consistently with the horizon/short as you step through the wizard

Calibration check

The Angular Distance app's default auto-calibration relies on manufacturer specs which on some devices may be incomplete or inaccurate. So it's advisable to check it, as is easily done by shooting a moon/planet sight from known position determined via GPS or otherwise. That is, when you set Assumed Position to match your actual position, the sights reduction  'intercept' becomes purely a measurement error. If the auto-calibration is healthy, this error shouldn't normally exceed 20 NM or so.

Bright stars at nautical twilight

As mentioned above typical device cameras do not capture stars very well in general. Nevertheless , the very brightest  (Sirius, Vega, Arcturus..) often capture reasonably well against the nautical twilight horizon, provided of course they happen to be not too high in the southern sky at that time.

Sun against artificial horizon

Where the device has corresponding hardware support, the Angular Distance app draws an artificial horizon over the captured image. With the caveat that its accuracy varies somewhat between devices, the artificial horizon makes it possible to measure altitude of the sun through a piece of welder's glass (cheap and easily found in stores), which otherwise conceals the visible horizon.

Note that the glass introduces a refraction error, which you can try to reduce by holding or mounting/clipping  it parallel to the device plane, and aligning the sun close to the center of the camera preview.

In pointing your device at the sun, never forget to be extremely careful to avoid looking at it directly with the naked eye !!