Insert comment form for single coupon post?

Hi
I am building my website https://www.affms.com/ using Couponpress
I would like to add comment form for the single coupon post?
I am using Wpdiscuz plugin and have checked the option allows Wpdiscuz display comment form for listing_type but it does not automatically add the form, I guess I have manual add the form code.

Which file I should edit to insert the code?

I am using Main theme of Couponpress and does not use any child theme

Thanks for support