Use the drop-down on the Owner, Tenant or Supplier list and select SMS (Text Msg.)
Make sure you select the person and there is a mobile phone number in the To field. Also, ensure the number begins with the country code prefix '+'.
Type in your message (The counter at the bottom right-hand side of the message box will tell you how many characters and texts you are using).
You can select a group from the Group drop-down box if relevant (i.e., if the text is about rent arrears you can link it to the rent overdue group).
You can also select a template from the drop-down box if relevant. (You can set up templates for the SMS, these are ideal for SMS texts that you send regularly. I.e., your rent is overdue).