To get started, navigate to the menu on the top left hand side of your device and Select 'Documents'.
Then select the relevant folder/sub-folder that you are looking to upload the file to.
Now select the 'Upload to' button at the top of your device.
Then 'Chose files'.
Select the document(s) that you want to upload.
Save the selection by clicking the 'Upload' button.
Now your file(s) will be stored within that folder/sub-folder.