Spine text is what you see when you store your disc on a shelf.
If you are using a graphic design program, you would embed your text into your design and upload it into the designated template for sizing.
If you're using our online designer - https://diymedia.zendesk.com/knowledge/articles/360011733053/en-us?brand_id=90547&return_to=%2Fhc%2Fen-us%2Farticles%2F360011733053