If you have suspected some suspicious activity on your Yahoo mail account and want to change your yahoo mail password immediately, just follow the steps, given below:
First, log in to your Yahoo account, using your username and password.
Then click on the account info button that will take you to the account info page. Where you have to click on the “Account security” option.
After clicking on the “Account security” option, you will see the change password option on the right side. Just click on it and set your new password.