If you have a local source for true essential oils, use it. Or order from me, or another online vendor. Check the Latin Name. There are other varieties of oils, similar to true lavender, that are sometimes sold as Lavender. They have different effects and won't be as effective.
Lavender is lovely in the bath.
Bottle these and let them stand for a week or ten days. A lavender bath will relax tired muscles and a tired mind. It's a wonderful way to relax before bedtime. Ten to fifteen drops of lavender mixed into a tablespoon of your favourite carrier oil makes a wonderfully relaxing massage oil. To induce restful sleep, put a drop or two of lavender on a cotton ball and tuck it into the corner of your pillow case.