A family of Microsoft word processing software products for creating web, email, and print documents.
Put the selection in an Endnote and then press CTRL+SHIFT+s which will cause the Apply Styles dialog to appear with the Endnote Text appearing in the Style Name control.
Then click on the Modify button and in the Modify Style dialog that appears, change the font to the one that you want.
Note, the Endnote Text is not normally superscripted. Looking at the title of your post it appears that you may be talking about the Endnote References in the body of the text rather than the text of the Endnotes themselves? If that is the case, select one of the references in the body of the document and follow the process described above to display the Apply Styles dialog and with the Endnote Reference style appearing in that dialog, click on Modify.