Error #200

Hi, my website is http://www.unapigraincucina.com
I get Error: (#200) Requires either publish_actions permission, or manage_pages and publish_pages as an admin with sufficient administrative permission”
I followed procedure indicated at this link https://docs.revive.social/article/926-how-to-go-through-the-facebook-review-process
but I have not solved my problem. Facebook asks to do other steps yet but I did not understand what I do. Can anyone explain in detail all the steps I will must to do?
The last answer of the facebook assistance is:
“Hello Tiziana,
Thank you for the information.
I’ve taken a look at the errors shown in your screenshot. Please make sure to set your app in development mode in the top right hand corner of your developer dashboard. Once you do so, you can use the Graph API Explorer to create a temporary access token to the manage_pages and publish_pages permissions to show the proper use case of the permissions in your screencast. You can find the Graph API Explorer here: https://developers.facebook.com/tools/explorer/.
To reiterate, in your screencast for publish_pages/manage_pages, please show the creation of the post in a custom composer (ie. typing it out), and then show that published post on the Facebook page that it is posted on (all in real-time). The review team will need to see the post on the Facebook page immediately after it has been published.
Please let me know if you have any more questions regarding your submission.
Best regards”