How to Wall run in parkour or freerunning
Don't just step onto the wall to begin the wall run. It is called wall "running" for a good reason! Plus, if you just step onto the wall from the ground, you won't have enough force to drive you up and along. You need to jump onto the wall if you can.
Try using your first step to take you vertical. Then your second step can drive you across the wall horizontally. If you have the height for a 3rd and 4th step use them going down.
DO NOT approach the wall on too much of an angle! This can lead to wall running on the sides of your feet and is very bad for gripping. Instead, approach on a more straight forward line and try to use the balls of your feet.