To ensure the highest quality print, please use the recommended image pixel at least 300 dpi. The nearer pixel it is, the better quality it will be.
You also need to set the color mode in your design file is CMYK to ensure the color in your product after being printed will be closest to your design.
The size of the design area/template file will change depending on the style and size of the product. You can check more about our template requirement for each product on our Catalogue page