How to Group SMS on an iPhone
Group Short Message Service, or SMS, texts allow iPhone users to send grouped text messages to contacts. Group messaging is convenient if you want to send the same text message to multiple contacts. Instead of having to send each contact the SMS message individually, group texting allows you to convey one message to a number of contacts simultaneously. Turn on group texting in the Settings menu to enable the feature
Open the "Settings" menu from your home screen of the iPhone.
Select "Messages" from the Settings page. The Messages preferences page opens.
Slide the "Group Messaging" switch to the "On" position. Press the "Home" button to return to your home screen.
Open the "Messages" application. Tap the "Compose" icon at the right of the top toolbar. The New Message screen opens.
Tap the blue "+" button at the right of the "To:" field. Your contacts list loads. Tap a contact's phone number to add the person to the SMS group. Repeat this step for each contact you want to add to the group. You can also type a phone number in manually; follow it with a comma before adding additional numbers.
Tap the text field of the New Message screen to type a message. The on-screen keyboard appears. Enter your text message.
Press the "Send" button to send the group SMS.