Most distributions* will allow you to install via an application called Synaptic or by using .deb (debian file). Please note that not all Debian files will work on all distributions of Linux. Although, you can always check out their website (the distribution's) to see what applications that can be downloaded and installed via a package manager (or do a simple Google search). Now, the best way to install anything on a Linux distribution is by using the SUDO command. Let me explain more on the SUDO command:
 
aptitude search = allows you to search through possible packages to install/download - after 'search' you should have some type of idea of what you want (example: aptitude search desk).  
 
sudo apt-get install = starts the installation process of the package you're attempting to download and use. whatever you get from the search, you should put after the 'install'.  
 
sudo apt-get remove = allows you to 'uninstall' the package you've installed. again, leave the package name after the "remove"
 
There are other commands, but I'm not going to get involved in them just yet... I'll probably add more to this later down the road.
 
 
*distributions: different styles of linux, different kernels and different style of running things.

David, you're an absolute failure. You need to go back to *nix School or something. You keep talking about how Windows is so much better - you got issues, son.