use of security answers when an email password has been forgotten?

Have same old Sky email address on iPhone and MacBook. The password for the email on iPhone is incorrect and not recognised, having 11 characters. The password used for the same email address on MacBook is correct and is recognised, it has 16 characters. I do not use Keychain.

How can I change the email password on the MacBook, then to use this new password also on iPhone, so they are both the same?

Both iPhone and MacBook have up to date operating systems.