I would say first make sure comments are enabled in “Settings > Discussion”
If that’s already enabled, then go to your Posts/Pages page, and click “Quick Edit” over each item. Then check the comments checkbox to allow comments on that page.
I have done that before. Please check my blog and you will see that at the end the word “Comment” appears.
What I want to do is to show at the end of the post the previous comments and the comments form.