Choose the template from the drop down box in Templates
Click on the Customize button.
You will get a warning about overriding but go ahead and continue.
Once you see your template in the textbox, you can then edit the template as you need to.
We always recommend that before you edit the file that you make a copy of whatever you see in that text box first (copy/paste it into file on your computer). This way if there is a problem, you can always put it back the way it was.
