Welcome to LQ!
If you just want to be able to download files remotely from this device, you can use ftp, scp, or ssh, etc. No additional programs are required. Your main challenge will be figuring out how to expose your machine to the outside world - you'll need to open a port in your router and/or firewall so that the machine is accessible. You'll probably also need a fixed IP address if you expect it work reliably.