How do I hear his/her/its words, though? I can't see anything without making it up in my mind... like, I cannot picture it being there without actually imagining it...

That's a tough one... Sometimes it will feel like tug on the back of your mind, and sometimes it will be pretty obvious when they are talking to you... The first time I met my guide, they wouldn't even tell me their name. But now I (on occasion) have full conversations with them.