Only Email/Print/Calendar admins and above can do this.

Note: Your members will need to verify their own number to be able to text them.

  1. In the side menu click Team Tools > Members.
  2. Select members(s) to text.  
  3. Click Communicate > Send SMS.
    1. Only those with a verified number will receive the text.
  4. Enter your message.
  5. Click Send.

Note: The parent accounts of members will be CC'd on all messages sent. If the parent does not have a verified number, the message will not get sent to that parent or member.

See Also
Send SMS Text to Accounts