Open the phone book and select the group you wish to send sms. Select the people within the group by clicking inside the tick box next to their name.
Click on the "Send SMS" button. You will be taken back to the "Composition" screen and the numbers you selected will be entered into the "To" text box.
Decide if you wish to keep a history of the message, if so tick the history box. If you wish to send the sms on a specific day, date and time it could be scheduled by selecting the appropriate options just before the "Send SMS" button. Once done, click on "Send SMS"