Unfortunately you probably can't. At least probably not the way you want.
When this system was designed Bose had multi-room based around cabled connections and as far as I'm aware, the other products to add onto that are no longer available. Partway through it's life Bose transitioned to SoundTouch for wireless multi-room. However you can't purchase the SoundTouch base separately (it was part of the Wave SoundTouch package).
The only way for you to do it currently would be with the SoundTouch Wireless link adaptor plugged into the Headphone out socket and have other SoundTouch speakers for the other rooms. The drawback of this is that if the headphone socket is being used you don't get sound out of the Wave at the same time (it's assuming you have headphones plugged in because you want to be quiet).