Hi alexplgr.

Go to www.another company.com > Select Updates or Select FAQS/Updates >  Register OR Sign In > Do you want to register another product?

Note: The Do you want to register another product? might be different if you have never registered with them before. I already have a lot of another company addons so that's what I see.

Doing this, they might inform Captain Sim that you have registered the 767 Captain Boxed product with them and Captain Sim will add it to you Profile. I'm just assuming that's what they do. But it seems logical to do it that way. ;)