You can import course source code built using the adapt framework or exported from the adapt authoring tool. However there are limitations depending on the version of framework and plugins that are installed in the authoring tool you are importing into.
The import feature does not "update" existing courses, a new course will always be create.
Import requires at least version 0.5.0 of the Adapt Authoring tool.
In the authoring tool, import a course by going to the dashboard and clicking "Import source" on the side bar. This will open the course import page.