Oliver,
Sorry for the delayed response!
API commands
Yeah, we need to put a document together about this. Fortunately, it's really easy. To add a user, simply use the following code:
Sendy::getInstance()->subscribeUser($email, $list);
Where $email = "
This email address is being protected from spambots. You need JavaScript enabled to view it." and $list = 2 (the list ID set in the Sendy System plugin, *NOT* the long string ID from Sendy itself.
Name field
As for the name, it seems like we're not setting that during registration right now. When we developed the plugin for our purposes, it just wasn't a field we needed since we don't merge names into our newsletters (mainly because Joomla is very lax about name policies and there's no way to separate first/last name).
That's something we may add in the future, and it's likely not difficult to do, but I don't have a timeline on when we'd do so right now.
I hope that helps get you going for now though,
Alex