Tell them to join TER the same way you did. That is as a basic member which is free to everyone. Then tell them to check out the "Self-Help Center" which can be found on most TER message boards by clicking on the "Self-Help Center" link (it's in teal colored font) found under the red and white life preserver near the upper right of the message board page. There is a lot of info there for providers and hobbyists. They will find the link for providers that explains how to get the free limited provider VIP mentioned by swimtrekr. All they need is at least one review and follow the instructions. There are very few reasons they wouldn't have TER access and they would only come into play if they had had access in the past and did something to cause TER to remove it.
It's really pretty simple. All it takes is a little time and reading.
Even if they don't have reviews they can still read here, learn here, and post ads here. Again all they need to do is read the "Self-Help Center".