In order to update a Canvas Commons course that you have already previously published, you will need to have saved the course in your Dashboard. If you do not have access to that course, you cannot update your Canvas Commons course.
1) Go to your original Canvas course.
2) Make all the edits that you need to make in that course and save.
3) Once you complete that, Click Settings.
4) Click Share To Commons.
5) A new window will appear and it will pre-populate all the fields for you to update your course material to the Commons Course since you already published it previously but you also want to add in the Version Notes what updates you completed. But first, make sure that these two things are completed: You want to make sure that the first check box "Is this an update to a previously shared resource?" is active and that the second option "Select which resource you are updating" has located the correct course you want to update. Then you want to
6) Scroll down to the section that says "Version Notes" and add in the box the changes you made or updates you added.
7) Then scroll all the way to the bottom and click "Update".