Dune 4K Pro has two built in OpenWRT torrent clients, Transmission and Aria2.
Connect the Dune to your network and find it's IP address (Settings - Information on Dune).
Then access IP:8080/cgi-bin/luci/ on a PC/mobile browser connected to same network.
So, if your Dune IP was 192.168.1.11, you'd type 192.168.1.11:8080/cgi-bin/luci/
You'll get a login screen like this:

No need to change user/password, just select Login (you can and should set a password after first login).
Transmission / Aria2 can be enabled and set up. As can Samba server, DLNA server, iTunes server, and much else.

To enable Transmission, go to NAS Services - BitTorrent and tick the Enabled box.
You can now access Transmission's web interface at IP:9091.
e.g, if IP is 192.1.168.11 it would be 192.168.1.11:9091
