Sitting on the floor place the tennis ball under one of your 'cheeks'. Roll gently onto the ball...breathe!
Bend the knee and drop out to the side. You can also move the leg around to adjust where you feel it.
You are in charge of the pressure. If it's too much then use your arms and the foot of your opposite leg (which is placed firmly on the floor)to take the weight off a little.
You are looking for a little discomfort so if there are a few spots that feel uncomfortable (NOT painful) then stay there and breath. You should feel the discomfort reduce. If it increases then move off and look again.
Stay on one side for around 60 seconds as you find a couple of different 'spots' to work on.
Repeat on each side 2-3 times. Little and often is best.