How to Customize Spreadshop and Spreadshirt Designs

How to customize the designs on Spreadshop and Spreadshirt.com. As shoppers, you have the option to modify designs and add text to most Spreadshop and Spreadshirt products. This is a fantastic option not found in most other Print On Demand (POD) marketplaces.
My Spreadshop: digital-studio-d.myspreadshop.com
Spreadshirt: spreadshirt.com