Well, first let us walk you through a process here. In Linux we enjoy having more information about a problem. Information is helpful in making solutions. So, please read http://catb.org/~esr/faqs/smart-questions.html
This will provide you with more background on how to find help.
Addressing your problem though. What version of Ubuntu are you running? Knowing this is important for knowing which repositories you can use. Repositories are like libraries of software for your distribution. If you get software out of the Warthog section of the library and you are using the Natty version of Ubuntu, there may be some conflicts.
Get to know Synaptic, Software Center if you prefer graphic package management. Packages are what repositories hold. Think of them as books. If you want to use Emacs for example, you look in Synaptic for the Emacs package, select for installation, click apply. Aptitude the back end command line version of Synaptic, normally invokes a mini-hacker named Casper. He's one of the good guys, think of him like the Window's set up programs. He puts everything where it needs to go for all users generally, which is /usr/share/bin or /bin depending the program.
Here is another good information source for you. http://ubuntuguide.org/wiki/Ubuntu:Oneiric#Package_Installation_and_Updates
This is for the latest version of Ubuntu.
To find out which version you're using:
Applications -> Accessories --> Terminal
Copy and paste the following to the terminal:
This will spit back a listing to you. DISTRIB_CODENAME will be what you want to check. The name after it tells you the version.
Further help is out there. Stop by http://ubuntuforums.org/
for example. Lots of nice friendly people able to help out. And there is lots more documentation available. Need to limit my time presently, minor physical issue causing pain from repetitive tasks, typing.