I understand that you are wishing to sync contacts from your computer to your iPhone 4S. Here is some relevant information on how to do so:
Contacts, Calendars, Bookmarks, and Notes
You can sync contacts, calendars, bookmarks, and notes with other applications on your computer. This allows you keep all your information in sync across multiple computers and iOS devices. The settings for these items are all in the Info tab for your iOS device in iTunes. With your iOS device connected to the computer, select your iOS device. Then click the Info tab.
"Whatcha gonna do Brother?"
Here is the way about how to transfer contacts from computer to iphone:
Step 1 Download and install the latest versions of iTunes (see link in Resources).
Step 2 Connect the iPhone to the computer using the Apple USB cable and launch iTunes if it does not start automatically.
Step 3 Click on the iPhone entry under the device list and then click on the "Info" tab in the main window.
Step 4 Place a check next to "Sync contents with" and then choose the appropriate email program from the drop-down list.
Step 5 Select all contacts or select individual contacts by holding down the Ctrl key while clicking on each contact name.
Step 6 Scroll down to "Advanced" and place a check next to "Contacts" under "Replace information on this iPhone." When checked, iTunes will replace the address book of the iPhone with the one from the computer's email client on the next sync only.
Step 7 Click on the "Apply" button when setup has completed. The contacts from the computer syncs with the iPhone during the next sync cycle.