Open the Create New menu by clicking the orange plus in the upper right corner:
Select Document to open the Uploader window:
Click the blue Upload button to select document(s) from your Computer or Dropbox account. You can also Drag & Drop files into the area bordered by the dashed-line.
Select one or multiple documents at a time (up to 20MB limit per file).
The transparent check confirms the documents have been uploaded. To view the documents and link them to transactions, click the green Go To Documents. To close the window, click Done.