Please keep in mind that very few oils on the U.S. Market are genuine and you should take extra care that you are taking oils that are not adulterated. The internal method should only be used by experienced practitioners. If in doubt, do not use this method.
Add a few drops of oil to a piece of bread, glass of water or juice, a small amount of olive oil, a small amount of honey, etc. and take internally. Only take a few drops at a time due to the potency of essential oils. There are many oils that should not be taken internally and some that are toxic when ingested. Again, this method should only be done by experienced practitioners.
Internal is one of the many methods of using essential oils.