Once users have signed up and the actual event has taken place, Admins will need to mark these users as Attended in order for the course to be Completed for the user.
Simply navigate to Admin > Learning > Participants List: here you will see all the different schedules which have been created. However, courses/schedules that have occurred in the past or that are currently in session will have been Archived.
Use the filter sidebar to filter on Status > Archived: here you will see past schedules.
Click the Hat against a specific schedule to Manage Participants List
You can now select users and click the Checkmark to mark users as Attended for this particular schedule