To edit Instagram account details from Facebook Page is very easy. Go Pages Settings.
==> Click on Instagram.
==> Click on Edit. Add or delete whatever you wish to change from your Instagram account details and click Save. That’s all.
NB: This feature won’t appear on your page if your Instagram account isn’t linked to your page. You cannot change your username, category, or private information on the page. You can only do so directly from your Instagram account.