There are five methods of adding learners to a course: the add learners widget, adding a learner from the course page, adding a course to a learner via their profile, via the API, and self-enrollment.
Add Users Widget
The first method, done via the course page, is the quickest method, but does not allow for Bulk Actions to be done. To add learners using this method, simply navigate to the Courses page by clicking on Teaching then Courses. Once there, click on the Add and Enroll Users to Course widget.
Once the panel pops up, click on the Drop Down menu and select the users that you wish to enroll.
You can do the same thing for Groups by simply clicking the Groups icon and using the drop-down menu to choose the group and clicking the Enroll button.
Add Users & Groups Tab
The second method, done via the course page itself, is very similar to the first method. The only difference is that you will have access to bulk actions. To access this, click on the course that you want to add learners to by clicking on Teaching, then Courses.
From there, click on the Users & Groups tab. You will see the exact same interface, with the addition of Bulk Actions on the top right.
Enrollment Via Users Page
The third method requires you to be in the Users interface. To access it, click on People then Users. From there, find the learner you want to enroll and click on the Graduation Cap icon beside their name.
You can use the drop down menu to enroll them in courses. Be sure to hit Update once finished.
Enrollment Via API
The fourth way requires some technical knowledge as it is done through the API (available to Premium and Enterprise clients only). The documentation for adding a learner through the API can be found here.
The fifth and final way to add users to a course is to have them self-enroll. Please refer to this article to learn how to enable self-enrolling.