A parent emailed me and asked what to do if her child's phone number wasn't appearing in the list of options. Follow these steps to address this issue.
Now on your computer, open up "Messages".
Next, click on "Messages" in the top left menu, and click on "Preferences".
When the "Preferences" window opens, click on "Accounts". On the right side of the window, click on "Add Email". Add your child's phone number is the following format: 999-999-9999.
You will then be prompted with a message about a verification email. This email will be sent to the phone
Email with questions! Happy Parenting!