Demikids (GBA) help

Hey, can someone tell me how to fuse demons in Demikids (dark version, if it matters). I know I've gotta go to those buildings with the pentagrams on the front, but I can't actually do anything in them yet. I'm pretty early in the game (just got to Centertown) but it's getting rough without being able to fuse demons/level up Gale. Any help would be appreciated.(disclaimer: yes, I did look around online for guides and haven't found anything, which is weird and makes it seem like fusion should be really easy to do.)

Neeeevermind, figured it out - you've gotta talk to the operator from behind the bench. Duh.