Just like when typing an SMS by hand to pay the parking fee, doing it via m-parking app also requires two basic information -- the car registration and the zone number. So, when first starting the app, those are the only things that need to be configured before you could start paying the parking fee.
Both of those steps are explained in following articles (Selecting a location & Creating a car entry). After that, the whole procedure comes down to just this: 1. open the app, 2. tap desired zone button, 3. done! That speed and ease of use are the principles the app is designed around.