Add your vanilla beans. You can split them with a knife down the middle, but I don't think it makes much of a difference.
Replace your lid, put a label on it and place it in a dark are where it will not be disturbed. Every week, shake the contents gently. After about 2-3 months it will be ready!
If you use some and want to keep it going, just add a little bit more liqueur and another bean. It won't really spoil because it is mostly alcohol. It will only get richer in taste with time.
Recipe by Saved By Grace at https://savedbygraceblog.com/make-vanilla-extract/