Visit http://a2d2.local on your phone, computer, chromebook, whatever!

Pick the brand of Smart Speaker you have in your home.

A2D2 Stream will discover what's on your network, just tap the play icon on the speaker you'd like to hear your A2D2 play through. 

It can take a few seconds to establish a connection.

A note on Apple Airplay:

A2D2's built-in AirPlay connection should work without a hitch. On some networks, AirPlay can't make the link between A2D2 Stream and the speaker(s) you want to listen on.

In that case, on A2D2's interface at http://a2d2.local there's a 'listen on this device option'. Go here on an Apple Device, hit play and then you'll hear audio through your iPhone. There'll be an AirPlay icon that you can select using Apple's interface to listen on the speaker of your choice.