In the Courses Menu, select the 'Search Icon' (top-right) and start typing the name of the course you're looking for.
If the course doesn't show up, you will see the option to 'Request Mapping'.
Besides the name and location of the course, input any additional information and tap 'Submit'.
Note: This is the procedure for new courses that aren't currently mapped at all in Hole19. For course update requests, see this article.