Footnotes or references in Scalar can be added as "Scalar Notes." Each note will have its own page. First highlight the text you want to cite. When you click on the Insert Scalar Note icon, it will bring you to the pages list. From here you can Create a page on-the-fly.
The title of the page will the the page's URL. The text will be note itself.
The new note can then be inserted in the text as a Scalar note. Alternately you could also have a reference list or bibliography as a page in your Scalar project and insert it as part of the path.