To use rosemary essential oils for improving your memory and supporting your brain health you open up the rosemary essential oil bottle and sniff it in through your nose.
Another way to use rosemary essential oils for improving memory is to mix some rosemary oil with some coconut oil.
Take 3 drops of rosemary essential oil and mix it with 1/2 teaspoon of coconut oil which will dilute the rosemary oil and then rub it on the upper neck where you'll be able to inhale in the rosemary essential oils.
You can also put some rosemary essential oil into a diffuser and breathe it in that way as well.