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
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.
<div id="main_body">Hello this is the main body</div>
Hope this helped