SuperSU undetected

I am new to this how do I add root support on khadas vim2 do I do this with a computer do you connect the vim2 to a computer what it is my vim2 is not rooted know more I don’t know how it’s happened but I click on apk SuperSU it says root undetected I see on GitHub do you download this zip file can you explain to us how to do this.

Sean