When it’s time to update your will, you don’t have to start from scratch. 
You can use a codicil, an addition or supplement that explains or modifies your existing will.

I give, devise, and bequeath $ ___________ to The National World War II Museum, Inc., 945 Magazine Street, New Orleans, LA, 70130, for its charitable uses and purposes.
In all other respects I ratify and confirm all of the provision of my said last Will and Testament dated on the _________ day of ______________, 20__.

IN WITNESS WHEREOF, I sign, publish and declare this instrument to be a Codicil to my last Will and Testament in the presence of the persons witnessing said Codicil at my request this _____ day of ___________, 20__.

_________________________ residing at __________________________ (name) 

Witnesses
_________________________ residing at ___________________________ (name)
_________________________ residing at ___________________________ (name)

The codicil, to be valid, must be signed in the presence of witnesses, and the original placed with your other valuable papers. A copy can go to your lawyer and a copy to The National World War II Museum.