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.