Boil the water till steaming, then fill a large bowl with it.
Add the thyme oil, starting with 10 drops.
Cover your head with a towel and hold your face over the bowl, allowing the towel to form a steam tent around your head.
Inhale and breath deeply and calmly. If the scent of thyme is not strong enough to make a difference to your sinuses add another 5-10 drops, as needed.