There are two basic choices, and professional assistance is in order for both:
(1) You can prepare and properly execute a new Will that revokes the earlier Will, or
(2) You can prepare and properly execute a Codicil to the Will. A Codicil is a separate document that adds to and/or replaces one or more provisions in an existing Will. It is like an amendment to your earlier Will.
While Codicils were often used in the past, now lawyers use word processing programs which are able to quickly integrate any changes you want to make — even minor revisions — into a new Will that is being brought up to date. The fee for such revisions is typically very modest, and the lawyer can suggest other possible revisions to take account of new statutes, tax regulations and changes in circumstances that you may have overlooked.