I'm doing seperate tutorials for Moya and Thunder.
MERGING LAYERS: #howtomergelayers
Go to the menu (hit the L button), then go to the box, bottom-middle, that says 3D. Select the layer you want, then click and drag it to another layer. Boom! The layers both hold the same image. Delete the first one (the one you dragged). If anything goes wrong, hit the R button to undo your actions!