For targeting specific areas sit in a chair, cross the leg being mobilized over your other knee and firmly press your unit by hand into your calf muscle. Direct pressure will be effective, but you can also experiment with twisting the unit to break up adhesions or gently shaking while maintaining pressure.
For more global calf mobilization sit on a workout bench or the floor, place the unit between your calf and the floor, and with a straight knee go through a series of flexion and extension at the ankle. Shift the unit up or down your calf and repeat.
To increase intensity bring your other leg on top of the leg being mobilized.