To enable to use embedded content within Salesforce, go to setup -> Salesforce CRM Content. Click the link to edit, then click the checkbox to enable.
Upon enabling, under Setup->Salesforce files you will see something like below, content permissions, etc.
Once enabled, search again for content and find the header "Content Permissions".
This area helps set up permission for a user to view/edit/add/delete a library content like document/files.
Written by Prabha Krishnamurthy