Page Layout The [File Widget] is available for Organization / Contact / Opportunity / Case. The way to enable them are very similar. In this screenshot walkthrough, we will enable it for an Opportunity.
Navigate to Account -> Setup -> Opportunity -> Setup Page Layout -> Opportunity Detail Page: Main Section
What just happened? If you clicked on the [Use Default Folder] link, you will see in the popup screen, which is just a regular file repository screen, that we just automatically created a ( Opp # ) Opp Name folder for you under the CRM Files folder, and linked it to this opportunity.
Click on the [Upload New Files] button to start uploading your files.