To do this, first make sure that you have a full size layer that is a regular layer, not the background layer. If necessary, convert the background layer to a regular layer by double clicking on the background layer and click Ok.
Now Ctrl + Click on the background layer which is the full size of the image. It should have marching ants around it. With this layer selected, click the layer that you want to center. The marching ants should be around the entire image but the selected layer should be the one you want to center.