Your Instagram account must be a Business or Creator account. Go to Instagram → Settings → Account → Switch to Professional Account.
Your Instagram must be linked to a Facebook Page. This is required for publishing via API.
Go to Meta Developers (developers.facebook.com) → Create App → Add Instagram Graph API.
Use Graph API Explorer or OAuth flow to generate a token with:
instagram_basic pages_show_list instagram_content_publish
Use Graph API:
GET /me/accounts → page → instagram_business_account.id
Paste:
• Instagram User ID
• Access Token
• Name
Add caption, media URL, and schedule time. The system will automatically publish.