If your speaking about getting the oil into a mist, into the air, use a diffuser. Good brands are Doterra and Young Living. The are probably the two of the best, or are among of a small handful of the best brands. They are not cheap, but due to their purity are effective in a medicinal way. Other brands are diluted and polluted, and won't work, It will seem like you are spending less, but you will actually be wasting your money, because they just won't do anything that essential oils are supposed to do.
You can use it topically, which is what most people do. Put a drop or 2 under and around each ear. Also some people apply it to the soles of their feet and on their spinal cord area.
Some people even ingest them. But if you do that, use only a drop. To much of them especially for a new user can overwhelm the body.
