Start by leaving the top of the bean intact, and split the bean down the center with a knife.
Open it up so you can see the black vanilla beans (it will look like coffee grounds). Leave each bean connected at the top so you can easily pull it out of the jar when done.
Fill the bottle with alcohol and shake, shake, shake!
If any of the beans float to the top, fill the bottle with a bit more alcohol.
Shake the bottle about once a week to help extract the flavor.
Notes
You can scrape out the insides of each bean and put it in the jar, then put the whole bean into the jar.
Alternatively, you can chop your beans into small pieces and place them in a mason jar and top with alcohol.
You can keep topping off the jars and do an always-renewing bottle of extract.
Continue shaking the bottle about once per week to help extract all the flavor.
Allow to infuse for 6 months, in a pinch you can use it at 3 months, but the longer the better.