The App has a tutorial video that demonstrates all of the following:
Seat Height: The top of the seat should line up with your hip bone. Turn the adjustment knob to the left, pull out and adjust. Then rotate the knob completely to the right to secure.
Seat Depth: (fore/aft) Find a comfortable distance that you have a slight bend in your elbows when holding the handlebars. As a guideline, the distance between your seat and handlebars should be roughly the distance between your elbows and tips of your fingers.
Handlebar Height: This is purely based on what feels comfortable and natural to you. A beginner would generally prefer the handlebars higher and a more experienced rider would prefer them lower.
SAFETY: ALWAYS MAKE SURE YOUR ADJUSTMENTS ARE SECURE BEFORE RIDING. THE POP PIN SHOULD BE IN A HOLE AND THE KNOB TURNED TO THE RIGHT TO TIGHTEN