I would say it uses windows media player to preview so you would have to set windows default sound device to UAD Apollo by right clicking on the speaker icon in the sys tray and playback devices but if you are using it with asio band in a box might take Priority ?
You can also run a line out from the internal sound card to the line in on the UAD Apollo.

Also you can use a virtual cable to mix sound cards to one output http://vb-audio.pagesperso-orange.fr/Voicemeeter/banana.htm