Enrolment

I have set up 2 Moodle courses. 1 is free, the other in paid. Both seem to be working fine. But - I want to enroll a couple of students for free in the paid course. ----Edited---

EDIT: OK I figured out that I can assign them a roll in the paid course, if they are already on my list of users from the Free course. Is this the only way? What if someone hadn't signed up for the Free Course first? Is there anyway that can be done? Or is it a good thing I have the Free Course, and I just need to tell anyone I want to give the paid course to for free, that they need to enroll in the free one first?

Thanks.