In order to add Seminar activities with Events to a course, the Seminar activity must be enabled on your site.
Site administrators can enable the Seminar activity from the Administration menu by going to Plugins > Activity modules > Manage activities. Here they will need to click the Hide/Show toggle icon (,
) next to Seminar activity so that the eye icon appears open.
The Totara Academy has a whole course dedicated to using Seminar Management in Totara Learn. Here you can learn more on how to use seminars, see best practice, and give it a go yourself.