How to Add "Quantity Button" on a debut theme

[imhomestore]

Hello,

I want to add "Quantity Button" to product page to let the customer choose the number of pieces they want to buy. How can I do that ? 

I have tried some solutions from your previous answers and it seems that the page/column you mentioned does not exist anymore.

I have included the latest debut page that you mentioned so you know the problem.

Thanks 

Denise