Oh my God!! I've also been trying to figure this one out for some time. I've even been looking for a tutorial on it for the last couple of days, but I couldn't find one. I was about to post asking after someone, but I figured someone would have already asked at one point. Sure, I'd seen the "Add To Library" button before, but I always figured that was for "install third party files now" or something. Maybe I'm just the slow one, but that really ought to be in the Poser FAQ.