Click Connect Facebook, sign in, and grant every requested permission — if one is skipped, publishing or comments will fail later with "permission denied". You then pick which Pages to connect; Instagram business/creator accounts linked to those Pages appear in the same list.

Instagram requirements

• The account must be a Professional account (Business or Creator) and linked to a Facebook Page (Instagram app → Settings → Business tools → Page).
• Personal Instagram accounts cannot be connected — Meta's API does not allow it.
• Images must be JPEG, up to 8 MB, aspect ratio between 4:5 and 1.91:1. Videos publish as Reels.

Facebook

• Text, links, single photo, multi-photo albums and video. Native scheduling lets Facebook itself publish at the time you choose (10 minutes to 75 days ahead).