Typically the roots are harvested when 2 or 3 years old. Older than that they get woody and difficult to work with, younger roots have not reached their full medicinal properties yet. Typically you will only find a tea or a tincture. If you choose to grow your own you can make your own tincture. 

You will need fresh or dried roots

80 Proof alcohol or an herbal vinegar 

1 pint jar

Fill the jar about ¾ full of fresh or ½ with dried roots

Cover with alcohol or vinegar and put a lid on it

Let 4-6 weeks strain and store.

 

General dosage is 1-2 droppers full 2-3 times a day for cough

You can use this as an external application for athlete's foot or other skin conditions.