In your course, click the Manage Learners button:
Select the Invite Learners tab to invite your learners to this course.
You have two options:
Invite by email:
List the email addresses of your learners (comma separated) and click Send. An email will be sent to the learners inviting them to self-register to the platform and join your course.
Invite with link:
Grab the link to your course and provide it to your learners. When they click on the link, they will self-register to the platform and join your course. Note that in this mode anyone with the link can join your course, while if you invite by email only the learners that you listed can join it.