Here are the steps to change your yahoo password
1. Login to your yahoo mail account
2. If you are on New yahoo mail interface follow these steps
I. Click on My account
II. Enter your password gain when asked and got to step 4
3. If you are on Classic view
I. Click on options
II. Click on Account information on the left side
III. Enter password when asked go to step 4
4. Click Change password under Sign-In and Security
5. Enter Old password and new passwords and click save
Or the simplest way go to https://edit.yahoo.com/config/change_pw (after login, or it will ask for login) and change password, i prefer you go with the above method which will avoid external site(even this site) links or copy paste this link to confirm that it is yahoo.