Hello everyone

I've finally gotten around to playing Kingdom Hearts again, and I'm officially stuck. At the moment, I'm in Hollow Bastion, I've just defeated Riku and found the pieces of the crest and assembled them. But now I'm really stuck, I'm not sure where to go or what to do, I've gone through the library and put everything in place too and been down to the Waterway - I hear you're supposed to meet Kairi there, but I haven't seen her.
Any help and I'd be grateful

-and as well, how and where do i get the yellow trinity, this is also slowly annoying me

Thanks agains
~*Crystal