These are the steps required to prepare a document for Design Online. Steps 1-3 happen on your local computer, steps 4-8 happen on the Designer server:
Once the variable data blocks have been added to the PDF template, the next step is to create and configure the product on the Designer server. The video below walks through steps 4-7: creating a new product, adding one or more PDF template files to it, and adjusting the optional text/image block controls.
Products are created within your Designer Admin account. Once a product has been created you can then add the necessary Template(s) to it.

See also
If you sell through WooCommerce, connect the WooCommerce Plugin next. Otherwise, continue to Testing a Product on the Designer Server.