The feature seems to be mostly identical to the already established "Spotify Connect" and its functionality.
To use it, you just have to click on the device selection in the "Now Playing" screen of the Tidal app – Chromecast devices already appear here, for example – and select the desired device.
At the moment Tidal Connect is already supported by devices from Cambridge Audio, Bluesound, Kef, Lyngdorf, iFi, DALI, NAD, Naim and Stream Unlimited.