Important: Only Brightspace administrators can add participants to a Sandbox Classic course.

From within your sandbox course, select the "Tools" drop down menu button, then in the "Tools" drop down menu, select the "Classlist" button

Next select the "Add Participants" drop down menu button, then select the "Add Existing Users" button. Ensure not to select the "Create and enroll a new user" button.

In the "Add Existing Users" section, enter in the email address, name or id number of the user you want to add. The email tends to be more reliable

Once the system finds the person, they will be listed in a table. First, select the check box for the person you would like to add, then select the roll you want them to have in your sandbox, then select the "Enroll Selected Users" button.