Hello there, HoseDwellers.
The following Knowledge Base article as a great step by step instructional on how to change the password for the account:
Resetting a user's password in OS X Lion and Mountain Lion
Important: Passwords for administrator accounts should not be blank.
- Log in with an administrator account. Tip: If you don't know the password of any administrator accounts, see "Resetting the original administrator account password" below.
- From the Apple menu choose System Preferences.
- From the View menu choose Users & Groups.
- Click the lock button if it appears locked; enter the administrator password.
- Select the name of the user whose password you want to change.
- Click the Reset Password button or the Change Password button.
- Enter a new password in both the New Password and Verify fields, and add a Password Hint if desired.
- Click the Reset Password button or the Change Password button.This should get you taken care of.
Remember, also, that you can restart the computer (you will be prompted to enter your administrator password) and this should log him out so that when you log back in, you can then follow the above steps with success.
Thanks for reaching out to Apple Support Communities.