If you have an air mouse (and if you don't have one, you should consider getting one) then keep holding down the ok button with focus on the icon you want to move.
Or are you using the stock out of the box remote?
You could also try a PC mouse if you have one.
Maybe the "mousey" bit has been disabled. From memory there is a button that switches mouse movement on/off (under and to the right of the ok button).
All i can add is that it worked for me without doing anything (and i use the nova launcher)
I have 2 boxes and 2 remotes.
One remote is the droidbox vip plus.
The older one is the droidbox s77 equivalent which they no longer do.
Both worked out of the box.
I didn't need to touch settings.
I notice in the version of android my box runs (5) under settings there is a "remote and accessories" tab. Remote is set to "off". Whether that makes any difference i can't say.
If your box has the droidbox share server app installed, you could install the droidbox share client app from the google play store on a phone or tablet and see if that allows mouselike control. I have tested this just now and it definitely allows you to drag icons around the screen on a nova wallpaper.