You simply let the app see your writing. When conditions are good enough it will take the picture automaitcally, clear it from background and straighten it. As if you've put the paper in the scanner.
The Whitelines Link system is a technology, available for paper and Whiteboard. You need the free app along with the hardware.
App available for google play and the App Store.
Print a paper and try it out; whitelines.se/link/print-papers/