The video below shows you how to go about the steps required

The Screenshots below shows you how to go about the steps required just as in the video above.

1 How to Put 233 infront of Numbers At Once

2 How to Put 233 infront of Numbers At Once

3 Correct Layout of Numbers to be Uploaded into Group

4 Save As Type CSV (MS-DOS)

5 Add Group

6 Group Added

7 Select Group and Click Import Contact

8 Choose File and Open to Import

9 Click Import Button to Upload Contacts into Group

10 Close the PopUp Screen and Click OK on Contact Added Successfully

11 Send Group SMS