Under Manage connected experiences, tap Story & post sharing.
Decide which account you want to control from your Instagram or Facebook account.
Toggle to automatically share your Instagram story or your Instagram posts on Facebook, or your Facebook story on Instagram.
Note: If you choose not to automatically share, you can still share individual stories or posts between Facebook and Instagram. Also, even if your accounts were previously linked, you may need to link them again in Accounts Centre to crosspost between Instagram and Facebook.