Step 1: Go to "Edit Settings" option from "My Courses"
Step 2: Select language from drop down menu in "Choose Language" under “Language” tab.
Step 3: Finally, Save your changes to your course and preview it to see the change in language.
Related Articles:
How do I set the time zone for my course?
How to re-order course chapters or pages
Do I get notified when someone takes my course?