Very frustratingly, the Knowledge Base says to use the chat box to private message other riders. I don’t see a chat box next to riders’ names. But then the Knowlwdge Base doesn’t show what a Chat Box looks like, so I’m not sure what I’m looking for.
This maybe be a good starting point for you: http://www.titaniumgeek.com/cycling/zwift-user-manual-unofficial-running-updates
If you’re trying to send a private message to other riders, you can only do that via ZML (Zwift Mobile Link), not within the game itself, and you have to be actively paired to your bike/trainer/sensors to initiate the chat. This avoids non-riders from spamming other people who _are _riding at the time.
To do that, just launch ZML, log into the app and choose the rider you wish to send the private message to. Once on their profile screen, simply choose the Message button and send them your private message.
In-game, the private message will appear in an orange bubble, vs. the standard colored bubble. If they miss it, they can pull it out of their chat logs later.