Hi Ernest!
You can enroll manually the users to the course, but this is not the only way to do that, i mean... you can use another enrollment method as self enrollment, cohort enrollment, etc.
Here you can read more about the enrollments: https://docs.moodle.org/37/en/Enrolments
By the way i can't see what version of Moodle you are using?, this is because you will need to select the version in the documentation.
If after you read, you have more questions. Let me know to give you more insights about your problems.
Best Regards
You can enroll manually the users to the course, but this is not the only way to do that, i mean... you can use another enrollment method as self enrollment, cohort enrollment, etc.
Here you can read more about the enrollments: https://docs.moodle.org/37/en/Enrolments
By the way i can't see what version of Moodle you are using?, this is because you will need to select the version in the documentation.
If after you read, you have more questions. Let me know to give you more insights about your problems.
Best Regards