You will need a 12 inch, (30.5cm) step. I stacked two yoga blocks. These can tip or be knocked over. You may use a staircase step and use the handrail for balance. Or outside there may be place in a park with steps. You may start with a lower step and gradually increase the height of the step. Move slowly be mindful to feel your whole foot on top of the step when stepping down and especially up. Carry your trunk elgonated and best alignment possible. If you have difficulty with bending at the ankle (dorsiflexion), perform a simple calf stretch. Soon, I will post a foot series to address the foot-ankle-knee.
Perform 10-15 repetitions on each side, two sets.