When you integrate Microsoft Dynamics CRM Online with SharePoint, you need to open related Sharepoint document by following steps;

1. Log on to Dynamics CRM Online
2. Go to Sales > Opportunities
3. Open any Opportunity
4. Click on "Documents" menu hidden in blue header menu on top of the Dynamics CRM Online window.

However, it takes too much steps to open SharePoint document, and reduces the user�s productivity.

So please consider implementing more easier way to open Sharepoint document.
Example of easier way:
1. Display if any related Sharepoint document is available for target Opportunity record.
2. If there is related Sharepoint document, you can just click on "Enable" button, and it redirects to certain Sharepoint document file's page.
etc..,