Depending on the page you are on, there are two different ways to view a document.
Homepage
On the Homepage, in the Recent Documents section, clicking any part of the row of the document you would like to view will open the document preview page.
My Documents Page
On the My Documents page, clicking the document name or ‘View’ button of the document you would like to view will open the document preview page.
Note: If the document you would like to view is not a PDF, you will need to download it in order to view it. Steps to do that can be found here.