Disabling comments on all posts/pages
Go to Themify > Settings > Default Layouts, tick the "Disable comments in all Posts" or "Disable comments in all Pages" checkbox.
Disabling comments on individual post/page
When adding or editing a post/page, there should be a panel called "Discussion". If the Discussion panel is not visible, scroll to the top of the page and click "Screen Options", tick the "Discussion" checkbox, now the Discusion panel should be visible below the content box, uncheck "Allow comments" to disable comments on that post.