You do not need to manually enroll users in your Blackboard courses.
Blackboard’s enrollment data comes directly from the University’s Student Information System and is updated several times each day. When someone officially enrolls in your course, that person is automatically added to your Blackboard course roster. When someone officially drops your course, that person is automatically removed from your Blackboard course roster.
Course roles control access to the content and tools within a course. Each user is assigned a role for each course in which they participate. For example, a user with a role of teaching assistant in one course can have a role of student in another course. The course role is set when a user is enrolled. It can also be edited after enrollment from the Control Panel.