Hi and welcome to the forums and to Ubuntu.
This being your first posting, and to Absolute Beginners, I assume that you are new to Ubuntu and probably to Linux. In the Linux distro universe there is absolutely no reason for new users to go outside of the repositories for their apps. This is just one of many bad Windows habits that it is important to break. Otherwise, you are inviting security nightmares.
To install LUA, it is only necessary to search for it in Synaptic and install. Since it is easier for us to help using the command line, just do:
We are invoking apt to first update your sources, and then install LUA 5.1. There are later versions, but they are not officially supported by Ubuntu 12.04 and you should not install them unless they have functionality that you cannot do without. Once you get better versed in Linux, that is the time to do more complicated things, but compiling from source for new users is just bad news.
sudo apt-get update && sudo apt-get install lua5.1
BTW, if you prefer using Synaptic, it is not installed by default in Ubuntu (a bad decision in my opinion, but it is what it is). To install it, do:
sudo apt-get update && sudo apt-get install synaptic