Its like any other software, just google how to run it on windows startup, there are several ways and google will explain it better than me.
Only question is doe desktop viewer start steamvr automatically and you might have issues if you try to run vorpx as admin as microsoft has made it all very clumsy for security reasons – some software doesnt autostart with some methids because of rights and whatsnot.
Start by googling something like “start program on windows startup” and see if you get it working first try, if not come back here and ask for more help. And remember – you still need a monitor plugged to view desktop in vr.