How to allow frame-ancestors for my Shopify site so another domain can use iframe to link

[FitBooks]

Hello, I would like to know how to allow frame-ancestors for my Shopify site so another domain can use iframe to link it. I am trying to advertise on a website but I can't because on my Shopify store, the frame-ancestors are set to none. I've had this problem for a while now and help would be appreciated.