Select the course you'd like to edit.
Click 'Edit Course' to start editing course contents.
Once you've done that you'll arrive at the course creation page which looks like this:
To reorder lessons first navigate to the lesson you want to move and hover your mouse over the 3 lines to the side of the lessons name:
Hold down the left mouse button and drag the lesson to the new location.
Release the left mouse button to confirm the action and to confirm the move of the lesson:
Your lesson has now changed location.
If you wish to reorder other lessons within a course then you can follow the same process for each one.
To confirm the changes you've made scroll to the bottom of the course creation page and select the 'Save' button: