Sara Wager explains in this introductory tutorial how APP works in a nutshell.
http://www.swagastro.com/astro-pixel-processor-tutorials.html
She shows you, how you can visually verify your light frame calibration using the dynamic light frame calibration in APP.
She further explains how you can see at what stage you are with your data processing and how simple it is to calibrate, register, normalize and integrate your light frames without having to save all intermediate steps.