Type the sentence that requires the superscript notation. This reference mark can be placed anywhere in the document, even in the middle of a sentence, but this can create a cluttered look. It is best to leave the citations to the end of a sentence, immediately after the period.
Insert the reference mark. In Microsoft Word, this is done by clicking on "References" in the horizontal ribbon at the top of the page and selecting either "Insert Footnote" or "Insert Endnote." Footnotes, as the name implies, allow you to enter text that will appear at the bottom of the page; endnotes appear at the end of the document section. The cursor will jump to that spot and you may enter in the text of your citation.
Click on the body of the document (above the citation) and you will be returned to the location of the superscript, which will appear as a small number slightly above and to the right of the sentence.
Enter mathematical superscripts without using reference citations by opening up the "Font" menu in the "Home" section of the horizontal ribbon. Click the box labeled "superscript" and enter your text.