First, go to the document page.
It should look a little like this:
If you click on the file name for a document, you will open it as if it were a link. Text documents will be saved, and pdf files and images will be opened. You can also right-click on the file name to select open in new tab to open it in a new tab.
From here if you wish you can also edit documents.
If you can't find the document you wish to view, you can search for it.