For what? The way to change the settings will be different for your bank than it would be for Google, or for logging into your Domino's account.
If this is about the Yahoo! Mail hacking issue, then you would go to Yahoo! Mail. Top right corner has a little spoked gear. Click on that, then choose "Account Info". Then choose "Account Security". You may need to enter the password. Finally, you should have access to change your password and adjust your security questions. Maybe even add a mobile number for extra verification.
Security questions aren't used anymore. DElete them. Your mobile phone number is your security.
Change your password and any other places you have used the same password.
go to Settings > Security Questions > Change
I have a horse!