MLA style is used to document sources in research and analysis. Any researcher must be able to document and cite the sources they have used to create their work. Every time someone does a research project, the idea is that they build on someone else's work, which helps to create and promote the progress of knowledge.
There are several places to find help with documenting a paper in MLA format. First and foremost, we have a page here at Enotes that will get you started. This page has all the basic information that you will need. Other places to look for information on MLA are Purdue's OWL (Online Writing Lab) and the Modern Language Association's website.
It is important to always have the format in front of you for reference. I always try to ensure my students are looking at the MLA source material so that they get the format right. It is impossible to memorize all of this information. Use the tools provided and they will help you tremendously.