What is the administrator password?

If you want to install program by graphical way, you have to insert the password that you have chosen at the installation setup.

If you want to install a program in the terminal, and you remember your password, you just use 'sudo' (Read here more about sudo: https://help.ubuntu.com/community/RootSudo). This will give you permission to do what you want on your system.
You have to put sudo just before a command in terminal and this command will be executed by the superuser.
For example, if you want to install vlc you have to use apt-get install vlc, but you need to be superuser, so the command will be:
sudo apt-get install vlc.

If you have lost your password please visit here for restore:
https://help.ubuntu.com/community/LostPassword

If you have solved this question, please mark as solved. And don't open more question. Thank you.

Though this is a bit late, I think it's still worth posting to clarify that eNry was saying that if you have one question open about a topic, you should not open additional questions about that same specific topic. You should certainly feel free to post other questions on Launchpad (just not more than one at a time about the exact same topic).