If you do not know How to Change Yahoo Password on iPhone, then to do it, follow the below steps:-

Step 1: Tap the Menu icon.

Step 2: If using the Yahoo Mail app, tap Manage Accounts.

Step 3: Tap Account info and then Tap Security settings.

Step 4: Enter your security code and Tap Change password.

Step 5: Tap I would rather change my password.

Step 6: Enter the new password and its confirmation and tap Continue.

If you have any issue regarding Yahoo, then you can call on ☎ +1-(269)-(409)-1989 to get support from  yahoo support team.