To set it up, head to the Conversations section of the Alexa app. Select "Contacts," then "My Profile." Finally, toggle on the "Send SMS" option.
To send someone a message, just tell Alexa to "send a text message" to whoever you have in mind. From there, Alexa will draw from your contacts just like she already does in order to make calls and send voice messages. Amazon says that there's no extra charge for each message beyond the usual voice and data limits of your wireless plan.
Alexa texts should work with all US carriers, but there are a couple of caveats to keep in mind. For starters, you'll need to be using Android 5.0 or higher, and you'll also need to be using an Echo device that supports Alexa messaging (the, the , the the or the ). That also means that third-party Alexa devices won't support the new texting feature.
There's no new Alexa app update needed to use the feature, provided you updated your Alexa app within the past month or so.
Amazon says that there's no plan to extend the feature to iOS users right now since Apple doesn't offer its messaging software to third parties like Android does. In other words, tough luck, iPhone fans.