That's very generous of you. Volunteering to be a donor is easy and can save lives.
The way to become a potential bone marrow or stem cell donor in the U.S. is to sign up for the National Bone Marrow Registry at the
Be The Match site of the National Marrow Donor Program. They send you a cheek swab kit. You swab your cheek to get some cells and then send them back.
See their list of
frequently-asked questions for answers to the questions people usually ask about joining the registry.
Once you are registered, you wait to see if you're called to donate. They let you know if a patient in need of a transplant matches you. If you're still eligible, healthy, and willing to donate, they make the arrangements and you have a chance to save a life.