Installing ZeroTier on ReadyNAS 104  upload failed

Installing ZeroTier on ReadyNAS 104  upload failed

I am trying to set up ZeroTier so I can access my ReadyNAS104 v 6.10.8  post  ReadyCoud withdrawn.

I have set up Zero-tier network and made active; my Remote PC (windows10), my Android phone and my local (to NAS) Windows 10 PC. But my attempts to install the ZeroTier on my NAS using admin have not worked.

I have downloaded to my Local PC ReadyNas /1.1.14-nt3  armel.deb version and  have accessed the ReadyNAS via Admin, gone to Apps and tried to upload the file but every time I try I get "cannot install application nastools -zerotier-one"

I think I now have to try using the root command but I am unsure how to access root on my NAS  and how to install ZeroTier on it.

Or, if this is a viable alternative, how do I roll back the firmware version to 6.10.7 so that I can upload an app (since I see that the app upload function no longer works in v 6.10.8 

My IT knowledge is next to zero, Can someone please advise me in terms of an idiots guide?