If you would like to change your Yahoo! password, just sign in to your Yahoo! account with your current password and click the Account Info or My Account link at the top of the page. You will be asked to re-enter your current password for verification. Then:
1. Click the "Change Password" link.
2. Enter your current password in the first box.
3. Enter your new password (as you would like it to be) in the second box.
4. Confirm your new password in the third box.
5. Click the "Save" button.