Social Publisher: Given URL is not permitted plus misc

Plugin Social Publisher settings:
I have the following error, in two cases:
1-in the Social Publisher settings, in the line below the 5 numbered one:
Associate your WordPress account with a Facebook account to publish new posts to your Facebook Timeline or Page.
2- in wordpress User, when you set your facebook field.

The error is the following:

“Given URL is not permitted by the application configuration.: One or more of the given URLs is not allowed by the App’s settings. It must match the Website URL or Canvas URL, or the domain must be a subdomain of one of the App’s domains.”

Now, I see that in the query is sent the URL of the wordpress site, i.e. my personal domain. Is that correct?
Reading the instruction I find very confusing the presence of 3 different sites, and often you don’t know which one to use:
1-wordpress site, or home domain, the one where you install the facebook plugin
2-host for the facebook app that you use to have the facebook plugin work, in my case is myapp.herokuapp.com
3-facebook plugin site https://developers.facebook.com/apps/xxx

Everytime they ask for a URL I do not know which one to use. Can you make it more clear in the instruction?

Also, do I need a https on my home domani? Where the wordpress is?
Or where the facebook app is hosted (heroku?)

https://www.ads-software.com/extend/plugins/facebook/