In this sig the guy cropped and made a banner that still included the image. How would I go about doing this? Do I go Image

Apply Image for the final image then crop it? Or do I crop it way before the final image is done?

Also, how do I crop? When I use the marquee tool and select what I want it does not work.. I only get what is selected. So instead I just selected what I did not want to be cut out and it still did not work.. I have a feeling it's a layer problem. Can anyone lend some much needed help? A detailed explanation would be really helpful. Thanks.