I received my certification in Aromatherapy waaa-aaay back in 1990 and recently went back to do some intensive study with Andrea Butje at Aromahead Institute. Boy, have things changed! The Essential Oils that have been around for centuries haven't changed one molecule, of course, but tons more great resources exist - there are apps and databases and forums that are amazing in content and depth.
There are also aromatherapy classes and videos available almost everywhere, but the one I really love is Andrea Butje's free online class, Introduction to Essential Oils. There are no catches, just good info.
Not exactly free, but very reasonable, is her book, Essential Living. I especially like the alternatives to toxic households cleaners.
One of the easiest ways to use essential oils around the house is to keep a bottle of Peppermint or Lemon EO by your sink and add a drop when you're washing dishes. Not only does that add antibacterial properties to the water, but it changes your whole attitude about washing up.
Another thing that's easy is to put a drop of Eucalyptus EO in your shower before you turn on the hot water. It's really invigorating. Dr. Bill Kurtin could probably tell you why it works on a molecular level, but, hey, I just like the quick wake-up.
Here in San Antonio, you can buy these EOs at Whole Foods and Sprouts.