Working Remotely

[ed]

You will need to connect to your NAS via VPN. This way it will be seen as existing in your local network even though you connect over the internet,
Here is a good tutorial https://www.youtube.com/watch?v=HF_VgvS90KA
Here is Windows https://www.youtube.com/watch?v=GRzwqBT0HXE

I hope this helps.