To change the footnotes globally:
1. Select a footnote individually (a gray box should appear around the note.)
2. In the Inspector, the window to the right of your document (if you don't see it: View>Inspector.Format), you should see menus options at the top for Text and one for Footnotes. Select the Text Inspector.
3. Select all of the text in the individual footnote you are going to modify and make the changes to the text of the footnote to reflect the new style you are trying to achieve (for instance, change the font to Times New Roman).
3. In the Inspector, in the Paragraph Style window (it appears just below the Text and Footnotes options discussed in Step 2), you should see the word: Footnote. Click on Footnote. This should open a dropdown menu. Scroll down to Footnote and click on the gray arrow to the far right of the row in the dropdown menu. Select: Update.
All of your footnotes should now reflect the new style that you were trying to achieve.
You can also modify a single footnote as described above. Deselect the footnote (e.g., select another footnote or the body text) and then reselect the footnote you previously modified. In the Paragraph Style window, there should be a blue button to the far right of the word: Footnote. Click Update to update the footnote style of your document.
Hope that helps.
Best,
Latavarius