The app guides you through. It tells you to hold the mic up in different positions around where your head will be in a box shape so it picks up the sound from all points around the head. You can widen the area too but try and be accurate from a central point. Imagine a large cardboard box around your head and measure each corner and areas with the mic.
You can name different settings so do one where you sit and then a wide one for other times if you wanted and switch them in the NAD app.