You can use the Accounts tab in the Setup group to change a user's password, or to prompt the user to change his own password at the next login.
To change a user's password:
1. On the Setup group Accounts tab, find and select the user whose password you want to change.
2. Float your mouse cursor over Password and select Change....
3. Type the new password in both the Password and Change fields.
4. Click OK to save the new password.
To prompt the user for a password change at the next login when the password is due to expire:
1. On the Setup group Accounts tab, find and select the user.
2. Float your mouse cursor over Password and select Force Reset. A confirmation prompt appears.
3. Click OK. When the password expiration interval elapses, the user is prompted to change the password at the next login.
NOTE: This feature is available only if you set the Forced Password Change Interval system preference to a value other than Never. Otherwise, the password does not expire and the Force Reset option appears dimmed.