You go like you would connect like normal. I believe a marry option will show up once they become good friends. (4 happy faces) So they have to like each other before they marry.
Humm... Um... Maybe they needs Hearts on the faces... They need to be smiling wide...I don't have two Tama-Go... But I do have two of a Music Star I'm basing this off of...
Usually there is Marry option in the heart icon when they are both of age. Humm.
I just read something about this in binary's log. Here, I'll link you to the post. Just scroll to the end of that post and binary has a list of how many connections he did until his 2 Tama-Go characters mated.