"Er wird das Kennwort gut sichern."
Just adding...It does not mean to make up a safe password which is not easy to guess. In this case the password is already existent and needs to be protected from others.
It means here:
to secure, to safeguard, to safely stow away, to protect,
(from other's eyes, ears, electronic access)
but when it comes to electronic access it can mean, don't leave the password on the same computer, put it in a hidden/encrypted folder, secret stash etc. :-)