Click on the Change Password link located above the Membership Information section of your Account Information page. You will be asked to enter your current password once and your new password twice. Make sure to click Save when you're done.

Please Note: To protect your account, make sure your password is memorable for you but difficult for others to guess. Never use the same password that you've used in the past, and do not share your password with anyone. For security purposes, your new password must be a minimum of six characters long. A good password contains a combination of uppercase and lowercase letters (remember that your password is case sensitive), numbers, and special characters such as $, ?, and *.

For additional information on choosing a strong password, please visit the Yahoo! Security Center.