You can enable auto-classification from 'API and Services' after you have upload at-least 20 documents on each document type enable in your account.
1. Enable documents from 'API and Services' or create new document type.
2. Upload at-least 20 documents on each document types.
3. Enable auto classification from 'API and Services' and wait for arounds 3 mins. Auto-classify is added to your document types.
4. Upload document to 'Auto-Classify'. Documents are automatically classified and extracted.
5. You can also added more documents and retrain by just disabling and enabling the auto classification API in 'API and Services'.