Where do I find Facebook page ID?
The best way to generate a content feed of a Facebook page is to use its URL. But also you can use page name or ID. When you visit a Facebook page you see its link. From this link, you can learn Facebook page name.
To find out Facebook page ID you need to have administrator rights to this page. Go to your page. Click "Settings". Click "Page Info". You will see your Facebook page ID there.