Want to center text or an image? It's very easy, REALLY! Just open up your image in Photoshop. Write your text. Select the layer you want to center and choose the Move Tool.

Now press CTRL A simultaneously. At the top of your Photoshop window, some funky looking boxes should show up. Your image should also be surrounded by a marquee.

To align your text/image vertically, choose the boxes on the left. To align your text/image horizontally, choose the boxes to the right.