For fromNotion to be able to grab the content from your Notion page it Needs to be shared to the web. Here are the 4 easy steps to share your Notion page and make it public.
Navigate to the Notion page that you want to turn into a website.
Click the «Share» in the top right.
Click the toggle to make the page shared to the web.
Copy the link that is now visible.
This is the link that you add to the fromNotion app. All child pages will automatically be shared to the web so you only have to do this step once with your parent page for fromNotion.
Let us know if you have any more questions.