When you say "Enrolling" have you already added the user to the site itself? If so then watch this video on how to enrol learners to your course. You have a new MoodleCloud site which uses a theme called Boost and this video is made with that same theme:
MoodleCloud
Enrolling Users in MoodleCloud
ການສົນທະນາຖືກລັອກ ດັ່ງນັ້ນ ທ່ານບໍ່ມາສາດຕອບກັບມັນ.