Once your course has been published, if your course is open to anyone to enrol on, it will appear on the Free courses listing on the site, so you can partly rely on search engines finding the course or people visiting the site and searching the list for courses to study, though obviously you can also promote the course yourself.
If your course is a closed cohort course in a private collection, you will need to notify the learners about it yourself. You can put some information in the private collection page which explains how learners can obtain the enrolment key for the course they want to study. You can also send out an email from you or your organisation to a group of learners with the following information in the instructions:
If you have sent out an enrolment key to learners, you will need to monitor who has enrolled on the course.