This tutorial by Sara Wager simply explains how you can create your master calibration frames in Astro Pixel Processor.
“This video looks at how you can create master calibration frames, ready to use in your final integration. I’ve created master bias, darks and flats in this video. Don’t forget that once you have created your master calibration frames, you can load in a light frame, click on l-calibrate and check how well the masters are actually working.”
There’s a very useful link about creating calibration frames on the APP forum…….