Brightspace allows you to add users to a course in bulk. Here's how you can do it:

Go to the course and click Users > Classlist in the navbar.

Click Add Participants > Import users from a file on your computer

On the page you are now, you will see the requirements the file must meet, and you can download a sample file.

Once you have created the file, click on Choose File and upload the correct file. Then click Import.

The action is being performed. You will receive a confirmation page that shows both the successful enrollments and any enrollments that were unsuccessful.