Hello, I want to ask how to make this edit box appear in full screen like https://fancyproductdesigner.com/product/shirts/

I try edit css but it not working and it only show like image

Try to change canvas size from product builder

Hello Manh Ta, 

You are doing it wrongly, You should try it making canvas the bigger from the FOOD Product Builder. Thanks

Im Done with this, thank you so much