How does iphone4s add contacts from SMS?

Iphone 4s SMS to add contacts is divided into four steps.

First, open the SMS and click "Details".

Step 2: Open the details and click the circled I next to the phone.

The third step is to open the details of the SMS sender, including adding existing contacts and creating new contacts.

Step 4: I choose to create a new contact here, as shown below, and finally click Finish to add it to the address book.