How do I hear audio from YouTube when I'm in GarageBand with focusrite solo plugged in?

When I am in Garageband on my macbook I am plugged into a focusrite solo and my guitar plugs into that. I use the Mac speakers for sound. This works fine. However when I still have GarageBand open and the focusrite plugged in I cannot go onto YouTube for example and listen to any audio. Is there a way I can get audio to work on both at the same time?