Adding rolling stock

If I wanted to add an engine or rolling stock and keep the engines and rolling stock this is already in Castle Rock
Do I use clone or new route
I do not want to mess up the one that came with my CD so I should not use edit route.
I have read the manuals over and over again but I have a hard time understanding them.
I upload an attachment and clicked on add to file I hope I did not miss a step or I will have to type another Q and drive you mad.
Do I use clone or new route

I have read the manuals over and over again but I have a hard time understanding them.

I upload an attachment and clicked on add to file I hope I did not miss a step or I will have to type another Q and drive you mad.