Q: I cannot install a  Mavericks software program on mac. it asks for administrator password. i never have set up an admin password on computer.

Not having a password means that any casual passer-by can have access to all your personal data, or deleting it.

Resetting or changing a password:

For Lion or later:  http://support.apple.com/kb/HT6022

If it's running Mac OS X 10.7 or newer, restart with the Command and R keys held down, open the Terminal, and use the resetpassword command:

https://discussions.apple.com/docs/DOC-4101

Well, you have to have set up an admin password to initially start up your computer. If you have installed the software before, it cant be the Apple ID password.

Are you referring to the password prompt from the app store before downloading? Every download/install of software from the app store requires your Apple ID and password.

The Administrator password can be blank. You can accomplish this when you first set up your mac you just hit enter when asked to enter an admin password. If that is your case, when asked for an administrator password just leave the field blank and hit enter. If it continues to ask for a password then you actually have set a password and you will need to retrieve/remember the password or reset it. Look here..... Mac OS X 10.6: If you forget your administrator password

Unfortunately, unless the OP's machine came with install disks (SL or earlier), s/he cannot use the instructions in your link. The instructions for machines that came with Lion or later were posted by Klaus1.