Because Hoppa works with Notion and maps its pages to internal data structure, Notion page should follow simple template, so structure can be correctly understood by Hoppa.
Here is how Hoppa's help center looks like in Notion.
As you can see, this is Notion's page, with more pages included. You can organize them by columns as you with: in multiple columns, single column, etc.
All subpages are organized by categories. Essentially category is a block with text above your pages, like in the example. Hoppa will see that there are some pages bellow this line of text, and will use this text as a category for them.
So Hoppa's help center looks like this for Hoppa:
Page you will connect to Hoppa must be publicly available on the web. All the pages within that pages should be available as well, but Notion will do that for you by default.
To make the page publicly available, open the page in Notion and click on "Share" (1).
Than enable "Share to web" (2).
After you shared the page to web, copy the link (3). Now you can paste it to Hoppa and emed Notion help center in your app.