Start by setting 4 points of contact to the wall: heels, bum, upper back, head
Set your arms in a 90 degree position with as much of your arms in contact with the wall
Before you start this movement, I want you to draw your belly button toward your spine and maintain this position
Now, extend your arms upward into shoulder flexion (keeping contact on the wall from every limb)
Control back downward to the 90 degree position, squeezing your shoulder blades together
Note: it is difficult to have all points of contact on the wall whilst keeping a flat spine, do not stress if you aren't there when you first do this exercise
