One course can have multiple versions. A new version of the course will be created when uploading a new entire course from a zip file like it was done on a new course. To create a new version click on the "Manage" link on one-course page:

Figure 1.10. 

Then click on the "New course version" button and repeat the steps for adding one course (The new version of the course will be the "LIve" one):

Figure 1.11. 

Figure 1.12.