You can either do this manually one by one or let them enrol themselves using an enrolment key or using a payment gateway like PayPal.
Alternatively, you can do this first by uploading the learners through the upload user feature in Moodle. You can upload as many learners as are allowed in your plan.
Once the users are uploaded and enrolled to the courses (csv file), they will be informed upon their enrolment into the courses by email. They can then access your Moodle site on MooDIY through the same site URL and using their own usernames and passwords.