To get started with LaTeX on Linux, you're going to need to install a couple of packages:
You're going to need a LaTeX distribution. This is the collection of programs that comprise the (La)TeX computer typesetting system. The standard LaTeX distribution on Unix systems used to be teTeX, but it has been superceded by TeX Live. Most Linux distributions have installation packages for TeX Live--see, for example, the package database entries for Ubuntu and Fedora.
You will probably want to install a LaTeX editor. Standard Linux text editors will work fine; in particular, Emacs has a nice package of (La)TeX editing macros called AUCTeX. Specialized LaTeX editors also exist; of those, Kile (KDE Integrated LaTeX Environment) is particularly nice.
You will probably want a LaTeX tutorial. The classic tutorial is "A (Not So) Short Introduction to LaTeX2e," but nowadays the LaTeX wikibook might be a better choice.
