The Modern Language Association (MLA) citation style is used mainly in literature and the humanities. If you're in a literature class, you might read a novella that you want to write about or quote from. In either case, you will need to include an entry on the Works Cited page.
Novella as Single Book
If the novella you would like to cite has been published as an individual book, cite it as you would any other book.
For example:
Johnson, Denis. Train Dreams [italicized]. New York: Picador, 2012. Print.
Novella in a Collection
If the novella is included in a collection, perhaps with other stories by the same author or in an anthology, the novella's title should be included in quotations, while the book's title should be italicized. You should also include the page range where the novella can be found within the book.
Roth, Philip. "Goodbye, Columbus." Goodbye, Columbus and Five Short Stories [italicized]. 1959. Boston: Vintage, 1994. 1–136. Print.
You can adjust the citation to account for specific circumstances. For example, the "Goodbye, Columbus" citation includes the date of the original publication after the title, but you might include the edition number or translator name here, if applicable. If you're citing an anthology, you can include the name of the editor after the title of the collection.