Instagram no longer requires that you have a Facebook Page connected in order to publish content using apps like Postpone. However, if you would like more in-depth analytics in Postpone, then you'll need to link your Instagram account to a Facebook Page. Here's how.
There are two ways to create a Facebook Page and connect it to your Instagram profile: either from Instagram or from Facebook.
If you do not yet have a Facebook Page then we recommend creating the Page and connecting it from Instagram following this article: https://help.instagram.com/570895513091465
If you already have a Facebook Page and want to connect it to your Instagram account then follow this article: https://www.facebook.com/help/1148909221857370
We also recommend watching the following 3-minute video for help connecting your Instagram Creator or Business account to a Facebook Page: