I was not sure if you were asking for help installing Ubuntu or adding software to Ubuntu. If you could clarify it would help. If your problem is when installing Ubuntu then their web site has some great instructions and installation notes. If you arew anting to add software to Ubuntu then the easiest way is through the software installer built into the OS.
There are several package management tools for Debian - based systems, most of which are based upon aptitude. There's the synaptic GUI tool and the command line tool apt-get. As a new user, you are best off using Synaptic.
before you install anything on Ubuntu, you should run on terminal "sudo apt-get update" it will help for dependencies.
For single *.deb file install --> sudo dpkg -i packagename.deb
For multiple *.deb files install on one directory --> sudo dpkg -i *.deb