I've got all the materials I need from the sable smithy, but I can't figure out where to go to combine them into a sword. Does anyone know? (sorry if this is obvious, I'm new)

You need to combine them at the Asmodeus Genetech Lab.

you have to go to Asmodeus Genetech Lab at the darkside but you will need to have all items in your inventory and at the lab it will say what items he needs.

Thanks everybody =)