Got it working. This case comes with all the fans routed to a central hub, and that hub is powered by a molex connection. The LED lights for all the fans and the rest of the case interior are all routed together as well, and are powered through a 2nd molex connection.
I had no idea what to do with the 2 empty molex plugs at first, because I had no idea what they were and didn't see any cables that would match their sockets. Thankfully my PSU came with 1 cable set that connects it to molex, guess I just didn't notice that set when I was sorting through cables during setup.
Now I have the fans connected to the PSU, but not the motherboard. Based on what I've read, there's no real benefit to connecting molex to a motherboard because it won't be able to vary fan speeds, and these fans are clearly visible from outside the case so I don't really need confirmation that they're working properly.