If you have forgotten the passwords to any of your accounts on a mac then you can reset them by following these instructions
Reboot your Mac and hold down ALT
When it shows all available drives, choose the Recovery HD, if you have set a firmware password, then you will need to enter that before getting to the available drives
When booted into the Recovery HD, click on Utilities and then choose Terminal
When the Terminal window opens, type the following
A new window will open, click on your System Drive and you will then be able to select any available account on that drive and reset the password for it
Please be aware that you will not gain access to the keychain for that account, so if you are after information saved in that keychain then you won’t be able to get it.