I only have small hands so tend to use one hand to keep the outer circle of the clear tube against the skin by holding fingers on top of the circle. Then I remove the clear elephant looking guard. I then use the other hand to push in the white applicator until it can't go any further with the click and then hold thumb over the white introducer and use fingers o to go underneath the clear circle and lever it upwards to the top. Press in the sides of the sensor and rock the applicator device forwards to make it come off. Insert transmitter and use lock key to hold the transmitter in the shoe ok. I sometimes use the lock key to lever the sides of shoe away from the transmitter and out it pops.