I haven’t tried this, but since Qnap is linux underneath, you should be able to get it to work like you would on any linux distro - if you can satisfy it’s dependencies, that is. Once you get it running, opening the app would be like the normal linux version, with http://:8080/razuna as base URL.
Question is should you run Razuna on a NAS? I think the answer to this is no. Razuna requires a relatively high amount of RAM - a resource that is usually in short supply on NAS systems. Unless you’ve got an (intel based) NAS with plenty of RAM, using the NAS as an target to store the data and running the actual code on another system would be a better choice. In this case, i’d suggest deploying it trough Docker or as a VM on the NAS, instead of trying to run it directly on the NAS system.