At this stage, the ProductPress plugin only works to restrict an entire page in WordPress, rather than just sections on a page.
However, when paired with the free plugin Restrict for Elementor, you can restrict access to sections of a page built using Elementor to only people who have paid for the upgrade via Gumroad or Paddle.
To do this, use the "Used with a specific capability" function, described in their documentation here: https://restrict.io/restricted-content-documentation/restrict-elementor-show-hide-content-users-specific-capability/
The capability to filter for is
productpress_XXXXXXwhere XXXXXX is the ID of the product at Gumroad or Paddle.
You can also view the name of the capability at the bottom of the User Profile page in WordPress for any user who has purchased that product, such as the one shown in the screenshot below: