MCEdit won't work

Ok, so I am trying to make a custom ore spawn in a custom dimension, the dimension is set to generate like an overworld, but the ores only spawn in nether terrain. I found a helpful guide, it told me to download the ore block as a mcedit schematic and have it generate in the custom dimension. I thought this was sound advice but when I opened the saves folder with mcedit the world I had put the ore in wasn't appearing. I tried dragging the folder over, and it appeared, but mcedit wouldn't open the folder. It may be because mcedit doesn't recognise the mods, but I was assured that this wouldn't be a problem.