You've probably done this wall Pilates move before without the wall. The wall can actually help make this move easier by giving you something to press against with your feet and can also give you some tactile feedback that makes it easier to engage your core.
Start in a high plank position with the balls of your feet pressing into the wall, about mat-width apart. Your shoulders should be stacked directly over your wrists, and your body should form a straight line from shoulders to heels. This is your starting position.
Lift your hips up and back into a Downward Dog, reaching your right hand back to tap your left foot, ankle, or shin (whatever is within your reach).
Then shift your hips forward and down, returning your right hand to the floor to come back to plank and return to the starting position. That's one rep.
Repeat, this time reaching your left hand toward your right ankle.