To add a footnote, the Markdown looks like this:
[^Name]: This is the text of the footnote.
1. In the Article editing screen, click on Show Helper
2. Select 'Add Footnote' in the dropdown
3. Enter the text you want for the footnote
4. Copy what is generated in the last box, and paste it in your article.
You can put an entire footnote directly in the brackets, and place this wherever you like in your article. Then in your app, at this place in your article, a small number will display. Tap it and the text of the footnote will show up.
Or put just a name in the brackets, to reference the full footnote elsewhere, perhaps at the end of the article. This could be a preferred way to keep your footnotes more organized. Then from the Helper, choose 'Add Footnote Reference' to create the full footnote. The name would be an internal reference. In your app, the footnotes will automatically be numbered and display as .. ..  etc.
For example, here is the footnote name [^FN1] in place inside the article, and then the full footnotes reference could be placed at the bottom of the article, to save from cluttering the content.
Check out our blog post on footnotes for more information.