Upload & Sell: On
Create a new document that is 8 x 20 at the same dpi as your existing jpeg
Drag a Guide to the center of your new document - it will "snap" to the centerline
With your original jpeg open, drag that jpeg into the new 8 x 20 document you just made. It will automatically make a new layer. Position that using Move tool over to the right side of the frame. It will snap into position with the guide you just made.
Select the type tool and use that to drag a type marquis on the left side of the frame
Type your text.
Use the text tools to adjust type size, spacing, kerning, color, font, etc.
All of your elements will now be on separate layers can can be moved and manipulated independent of each other.
Save your file as a tiff with layers intact
Duplicate the file. Flatten. Print. Or whatever else you want to do with it.