On each of the profiles, click the privacy tab and scroll down to where it allows you to add members (Enter someone's e-mail address to add them:). You will need the email your friend used to join WT. Simply type (or paste) the email into the place for it, then click the big ADD THIS PERSON button.
Hi Bob. If there are a lot of profiles, you can use the Bulk Trusted List Change form. See
I hesitated to recommend the bulk add function, as I've seen more than one g2g post saying the person got added to thousands of profiles and had only asked access for one. For me, for "safety", I would do one at a time unless it's into the hundreds of profiles.