Want to install programs you want, but because you are new to Linux, don't understand how it works? This article will show you how to install simple programs in Ubuntu.

[edit] Steps

Connect to the internet unless you are using offline repositories.

Through Package Manager

Open your main menu, select System, click on Synaptic (or Adept Updater, depending on your distribution).
Type a query into the search
Select a file you think is relative to what you want
Click "Install"

To do Manually

Open up terminal (Konsole, xterm, or any other command line/bash shell interface)
Type sudo su (sudo as in superuser do, su as in "switch user") to get administrative privileges to install software
Type your password if prompted.
When it gives you a new cursor after something that looks like this, "root@computer:/#" where "computer" is the name of your computer:
Type sudo apt-get install but don't hit enter! You need to know the package name of your program. "sudo aptitude search <program>" will yield search results for your package when you supply it to the terminal. In some cases, it may automatically know which package you want, such as "sudo apt-get install firefox" Look on the package page of the Ubuntu distribution site.
If you are not sure of the name of the program you are trying to install, you can use tab completion to try and find it (most major distributions have it.) Simply type the first few letters of the package you want to install and hit tab once or twice. For example, type fire and then hit tab, it will bring up all packages that begin with fire; firefox will be one of them.
Wait for it to prepare to install the software package from the repository.
If you are prompted whether or not to install, type "y". Next time if you would rather have it do it automatically, type sudo apt-get install package -y, package being the name of the package you are installing.
Wait for it to finish installing, and close the terminal.
It should be in the Main Menu under the appropriate category. If not, restart your computer.

[edit] Tips

Try to install only packages you will use
Update your packages by typing
sudo apt-get upgrade or sudo apt-get update
If you decide you do not want a package anymore, type
sudo apt-get remove packagenamegoeshere
where packagenamegoeshere is the name of the package.
If you are making changes to your sources list (/etc/apt/sources.list), be sure to update it with sudo apt-get update.
When you install a package, other packages may be installed with it as well. These are called dependencies.

[edit] Warnings

Don't run programs that can crash the system (Won't crash like Windows, of course)
Be sure whether it is the correct program you want. If you don't download the package from the main distribution site, the package you are downloading could be porn, which is not what you intended. Be sure you trust the site that you download from.