Get some eucalyptus leaves – you can collect them yourself from the trees, dry them and keep them in a jar, or buy them. Bring some water to the boil in a large pot. Add the eucalyptus leaves. Let the pot boil so that the steam fills the room. Alternatively, remove the pot from the flame, cover your head with a towel and hold your face over the pot while breathing deeply.
You could also add 10 – 15 drops essential oil of eucalyptus in boiling water and breathe in deeply, or have a hot bath adding water in which you have boiled eucalyptus leaves.