File Sharing from File Station

[Skeptical.me]

I'm just wondeing how to share files from my NAS externally.

1. I have my ISP's Modem/Router at the front of the house.
2. I have a ASUS RT-AC87U Merlin Firmware in my bedroom
3. The NAS is connected to the ASUS Router
4. I am running QVPN Client using ProtonVPN
5. I'm guessing that I have to share via cloudlink, or myqnapcloud

Is there a guide or has anyone got any suggestions to help me out? Pointing me to a guide would be great.

Thank you.