Create a division (div id="name-here"), then for that division use that image as the background
. Then you can type and edit it through the HTML page rather then having to open Photoshop and change the text and re-save.
Example code would be something like this:
background: url('background_main.gif') <-- this sets the image as the background for that division
<div id="main_body">Hello this is the main body</div>
Now the text "Hello this is the main body" would appear on top of the image. Generally, I create another division for the text, so I can give it margins and padding etc.
Hope this helped