File Repositories: The "Code" Tab

The “code” tab contains a list of all files related to the repository that have been uploaded and contains the “Read Me” section of the repository. Generally, any schemes, images or documents related to the repository should be uploaded to GitHub.

File Sharing (Web)

You can upload files by clicking the “Add file” dropdown and choosing “Upload files”. To download files, navigate to the appropriate file and click “Download”. If you are editing a downloaded file, it must be renamed before re-uploading.

File Sharing (GitHub Desktop)

A more powerful option for file sharing is to use the GitHub desktop application. This duplicates a copy of all the files in a repository on your computer and allows any edits or additions to be synced back and forth easily, a little like Dropbox. This method also eliminates the need to rename the file, saves version history, and allows a double check before major changes are made to a file.

To add a repo that exists in the web already to your GH desktop: Go to the “code” tab and click on “Code” at the top right. The “clone” button will add the repository to your GitHub desktop. You can also open GitHub desktop through this menu.

GitHub has more detail about this here.