You don't. Route builder says
Create routes that later on can be used as filters in some pages.
Therefore the route builder does not create a cache list, but only a virtual "area", which you can use to filter in the other tools. for example MapCompare, where you can select "Route" to filter the caches.
The next step can be adding the filtered caches from there to the VirtualGPS just by selecting the caches you are interested in (or all) and clicking the "Add" button.