You will need to be signed in as a teacher.
To invite members to a course, click on your profile on the top nav, and after that click on 'Manage community' on the drop down menu.
You can send the link to the new members of the course for them to be able to access the course content; or you can send them an email invitation to the course.
Select the account type for each members;
The account types are:
Style the community with a header image.