MLA is designed around the idea of containers. For example:
You can see how the containers work in the template below, which shows how to cite a newspaper article found in a library database (ProQuest). Sections 1-2 are core elements. Sections 3-9 are the first and second containers. You fill in the template with the information available. That information will differ and vary depending on the type of source you are citing.
To guide you through the process, MLA has created a practice template (and linked on the next tab).