First picture: I jump up against the wall with both legs at the same time. They remain bent. (As I am not yet able to do it, I went first in handstand and bowed them later, but this is not the goal of this exercise). It is important that the distance is far enough from the wall. The next step is to bend the hips. The arms are not straight up but in an ankle to the wall. This is why you need room. To take the knees under the armpits is the goal. Bandhas might help. It is important I think to be in control of the movement.
It is difficult for me, but I try. My first step is to lose (Anna!!! my teacher) fear. I'm just learning to jump up with both legs with both legs bent.
Studying the pictures I saw how important it is to go forward with the shoulders without losing balance. the arms are straight but not 90 straight up, but in an ankle to the floor (or the wall).