I really don’t find anywhere on the website where it tells me how to operate the Bridge II with an app. I see a blurb that MQA, Roon, Tidal, Spotify, VTuner are all new and supported but nowhere do I find how to use these?!
Just one of the options (install mControlHD for tablet). With Android i recommend to use BubbleUPnP 
For Spotify just install and launch the Spotify app (computer, tablet, phone). Click on Devices (bottom right, next to the volume slider, on the Mac version) and select the Bridge.
Just a note, you must have Spotify Premium, free won’t allow the connection.