In case you are able to sign into yahoo then you may change the password by following the steps below.
• Sign into your Yahoo account and click on your name tab.
• Click on the “Account Info” button.
• Next, go to the left-hand side pane and click “Account Security”.
• Enter your current password one more time (if required)
• Click on the “Change password” link from the upper-right side corner of the page.
• Enter a new password twice and click “continue”.
• Finally, click on the “Looks Good” button.