The password you need to enter is the Mac OS X administrator password for your computer.
When you install new software onto your Mac OS X computer you will be asked for your Mac OS X administrator name and password. Mac OS X will ask for this password or passphrase during any installation process so that unauthorized changes can not be made to the system.
The user account you created when you set up Mac OS X is also the computer's administrator. There may be additional administrator accounts created on the computer, depending on how it was set up. You need to enter an administrator name and password in order to proceed with the installation. If this password has been lost, you can search Mac OS X Help for information on how to reset the Administrator password.