According to the documentation, it supports Windows file sharing (SMB) and FTP. So you should be able to address it accordingly.
\\192.168.1.1\<share-name>
(try \\192.168.1.1\public, a reviewer @ Amazon mention that share specifically)
ftp:\\192.168.1.1
Assuming 192.168.1.1 is the router's IP address.
I have no idea what the default security is, if any.