I've found several different kinds, using pretty much any carrier oil you'd use in making your own beauty products. For example coconut oil, avocado oil, almond oil and so on. I use olive oil because it's what I use have on hand and is relatively cheap although I would like to try coconut. Here's what I do... take about an ounce of oil, slightly more for longer hair, I add my staples lavender and peppermint oil just a couple drops of each. Lavender is relaxing and peppermint helps with my dandruff. Put the oil in a glass container, I use an old olive oil jar, then place the glass in a bowl of extremely hot water, not quite boiling but close.
I wash my hair, using as hot as I can stand water to rinse. Then apply the oil so that there is a light coating on all my hair, I usually start at the roots and massage it in to my scalp as well. Once all my hair is covered I put, now this is going to sound weird but bear with me, a plastic grocery bag over it if you have one use a shower cap. Just your hair! Not your whole head. Then wrap a towel over that. Leave on for 30 minutes, then wash out. You might need to wash your hair twice to get all the oil out. I usually use the Vinegar Hair Rinse at the very end. My hair much more silky and manageable after doing this.
Note: I am not a professional and this is based on what I did and what worked for me. What works for other folks isn't the same. Please use care when using essential oils and keep all the ingredients out of the reach of children.