Carefully follow the instructions on this page.
When you set up the folder for your repo, make it a direct sub-folder of the Fargo app folder in Dropbox. This is important. It must have the same name as your repo.
There's a new directive, #siteFolder, that allows you to tell Fargo where to store your files. This is how I set it up for the Kim Parker site: #siteFolder "scripting.github.io/kimParker/"
When you're ready to try it out with Fargo content, render the whole site with the Render All Pages command in the File menu.
Verify that the pages were rendered into the sub-folder of your GitHub folder.
In the GitHub client, click on Commit & Sync button. Screen shot.
View the updates on your website.