Open the Messages app
On the watch, swipe to the first page of apps and tap on the blue messages app. This will display the approved contacts that the watch is able to message.
Send a text
To send a text, tap the white "T" button on the bottom left corner of the screen. Here you have the option to type out a custom text message, select an emoji, or select one of the preset text messages which you can customize in the parent app.
Send a photo
To send a photo, tap the gallery button at the center of the bottom of the screen after you've selected who you want to message. You can then choose a photo from your gallery, or tap the red camera icon to take a new photo to send.
Send a voice message
To send a voice message, tap the red microphone button on the bottom right corner of the screen. You can record an existing voice note with the red "New note" button, or send an existing voice note by tapping on the note, and then tapping the blue send button.