Can't change password to another password?

I need to make my Virtualmin root password more secure but I can’t change it?
I tried to SSH into Virtualmin, but am unable to.
Any help?

Your virtualmin root password is the same password as your linux password.
Connect with SSH to your server with your user account (not root, if you can do that, change your settings later)

user> su
user> root password
root> passwd
Changing password for user root.
New password: enter password
Retype new password: enter password