To add learners via API, You will need the participant's email address, username, or API user id. Precisely as in the admin view, you need to add the participant to a course and then activate them.

POST /orgunits/{orgid}/projects/{projectid}/participants - Add participantPOST /orgunits/{orgid}/projects/{projectid}/participants/${participantId}/activate - Activate participant

The next step is to set up an automatic email in Learnifier, such as an invitation email that can be triggered when a participant is registered. Please see How to get started with automated communication or contact support@learnifier.com to learn more about automated communication. The full API documentation is available here.