This article describes the benefits of essential oil, the ways in which the oil can be applied, and how to use essential oil safely. Depending on the type of oil and the desired effect, an essential oil is inhaled, applied to the skin, or ingested.
If you plan on using essential oils a lot, I recommend installing an app on your smartphone. You can find a lot of guides on using the oils, as well as apps with recipes to make blends.
Of course, you can also find this information on the internet. I have the app of Young Living and I like it that all necessary information is easily available, independent of where I am at that moment.