These tutorials, provide a hands-on introduction to LaTeX. You will see, the usage is very simple. Even if you have only used word processors (e.g. Word) before, you can learn LaTeX in no time.
In the following lessons you will be introduced to all the basic features of LaTeX, one feature at a time. As a beginner, you should either start with the first lesson or, if you just want a very brief introduction, try the interactive quick start guide. While the beginners course will enable you to typeset your research papers or thesis, the advanced lessons will introduce you to very powerful features, which are a bit harder to grasp, but can boost your productivity.
You can try out the mathematical typesetting engine directly in your browser. I've set up a sandbox
for you to try it out.