Go to the Utilites menu and select Terminal
At the prompt type ‘resetpassword’ (hit enter)
you will see Reset Password ***** select the Hard Drive in the top part of the window pane, then select the user that you need to reset select the account in the lower part then add and confirm the new password ***** click save, you get a confirmation screen and details about the keychain account.
Go to the Apple Menu and click Restart to boot back to the normal hard drive and the new password ***** take effect.
Sorry Reboot into the Recovery HD by choosing the ‘Apple‘ menu > Restart, then hold down the ‘Command’ + R’ keys on the keyboard during the start up process. When you see the Apple Logo you can let go. When the machine boots you may have to choose your language then you will see the OS X Utilities screen. Then follow the above directions.