If you want to edit your published course, go to the Assigned By Me tab in the My Courses page. If you want to edit an unpublished course, go to the Authored By Me tab in the My Courses page. There, click on the course you want to edit. The course page opens up. You will see the Edit button on the top right corner of the page. By clicking on that, you will be taken to the course creation page. Here you can make the changes you want to make.

*Please note that after you edits the course you will get an Revert Changes/Update button at the top right corner of your screen. Click it to update button to update the course.