How to access NAS540 from any WIFI

[Luxliev]

I'm new to network storage and I need help. I have no problem accessing files from the same wifi connection that NAS is connected to but how can I make it possible so I can access NAS540 from any wifi connection.

some of the settings that I have currently if you need info on any other please let me know

UPnP


PPoE


FTP


Web Publishing


WebDAV


I'm looking for easiest and most secure option

 

[Luxliev]

No one?