WhatsApp web option not displayed in WhatsApp iPhone I have an iPhone 4S with WhatsApp.

I install WhatsApp Web on my PC. It starts, and displays a QR code.  I'm supposed to use my iPhone's WhatsApp to scan the Qr code. The menu item to do this is supposed to be in "settings". When I open "settings" I don't see the option. It's supposed to be below "tell a friend".



What do I need to do to get the option to appear?

The option should be appearing in the iPhone software "WhatsApp"; it is missing from that software as installed on my device.
It seems that you have an old iOS version on your iPhone. In order to use WhatsApp Web, you should have at least iOS 8.1 installed on your iPhone. (https://www.whatsapp.com/faq/en/web/28080003)

In order to update your iPhone, go to Settings > General > Software Update > Install Update.