How do you change a beneficiary on a Will?

You can either redo your entire will or you can draw up what is called a Codicile to your existing will.  A codicile changes or adds a provision to a will but allows the rest of the will to remain the same.  You should see the attorney who did the original will about doing this, to make sure it is correct under the law of your state.

You need to contact an attorney licensed in your state.  All states have strict laws imposing very strict adherance to their rules.  Wills historically cannot be changed in any way without jumping through procedures set forth by statute in your state.  To my knowledge there are no states that do not require execution of a document that is signed in compliance with the state's requirements for signature and attestation by witnesses.   You may have to execute a new will, or you may have to execute a different document to achieve your goal.   If you fail to follow your state's requirements, your attempt to change the beneficiary will not be recognized as legal.   In Washington State, the law requires attestation by two witnesses who meet competency requirements.