To set up the course to use the group enrolment keys rather than the course enrolment key:

Go to Course administration – OpenLearners – Enrolment methods

Hide ‘Self enrolment (OpenLearner)’ and Guest access. Click on the edit button for OpenLearn Enrolment.

Click on the editing button for ‘OpenLearn Enrolment' so the editing form appears

Where it says ‘enrolment key’ insert the enrolment password for the course (like the group enrolment keys, it should not be too easy to guess).

Set ‘use group enrolment keys’ to ‘Yes’. This will activate the group enrolment keys to use instead of the course enrolment key you have just entered (which is still needed as part of the settings but is not needed by the learners). Make sure the default assigned role is ‘OpenLearner’.

Save the changes.

The learners will only be able to enrol on the course with the enrolment key you send to them for their cohort. They will only need to use the enrolment key once, unless they unenrol themselves from the course accidentally and want to enrol again.