Custom product dca fields (not attributes) from module

Customs tl_iso_products fields from custom module are not showing. That is actually, tl_iso_products pallettes from custom module is not considered.

So I have this ticket opened.
https://github.com/isotope/core/issues/1061
Above ticket is closed with answer:
"Palettes for Isotope products are defined in the product type. You can enable your custom fields there."

I have tried it there inside ('tl_iso_producttype'). But I can't get it working. Can some one show me how is it possibly done.

Thank you.

I did not mean the DCA, but in the backend configuration.

Thank you, I understood it now.