Enrichment takes place on the item page.
First, find an item (a single document) you want to enrich by searching and browsing the project collection on the Discovery page. Click on a story (1) and select an item from the story page (2), or select an item directly from your discovery results.
You can only add new enrichments to items marked with the grey (Not Started) or yellow (Edit) statuses.
Tasks for items in the orange and green statuses are explained in the Review section of this tutorial.