Installing sudo package on the LAMP server

Hi there --

I have completed the installation of the LAMP server, and one package that I am hoping to install is the sudo software. I want to be able to have a non-root user be able to run commands. When I entered the command apt-get install sudo, the package could not be found by the system. I have confirmed the system has the ability to access the Internet. 

Do I need to modify the available repositories, and if so, what are the file(s) in question, and what is the correct syntax needed here?

Thanks.