You will need a black background, add your image, then put it in the center of the black image. Then Create a layer. Layer > New Layer. Use the bucket and fill the layer with black. Set the last created layer on top of the other 2. Set the last created layer's transparency to 60%. (Double click the layer in the layer window, and set optacy to 60%) Then use the Select tool (The box icon that is made up of lines) and select the area on the transparent layer that your picture is on and press delete.