Just as you cite journal articles, websites, and any books you reference in your publication, so too do you need to cite any data your publication uses.
Citing datasets, such as spreadsheets, interview transcripts, images, etc., is crucial in providing context for your research and giving credit to the individual who's data you've used.
A dataset citation includes many of the same components of a traditional citation.
Many style manuals have not developed specific instructions for citing data. If the style guide you are using does not address data citations, you may use the basic citation elements, regardless of the type of work.
Joint Declaration of Data Citation Principles, Feb. 2014
Image source: Joint Declaration of Data Citation Principles
For a complete description of data citation guidelines refer to pp. 210-211 of the Publication Manual of the American Psychological Association, 6th edition
Since MLA has not developed a specific citation style for datasets, the general rules for citing a web document may be applied.