Can't get on internet unless using Wi-Fi?

Recently I got a iPhone 5 today, and I can't get on internet unless using Wi-Fi? Someone said to go to: Go to Settings > General > Cellular > Turn ON cellular data… But I don't have any of that please help

Make sure you sim card is installed properly and then reboot the phone by holding in the home button and lock button in at the same time. Then go to Messages>(supplier)> and follow there instructions. If there's no message go to SETTINGS> GENERAL> MOBILE DATA (ON)

ENABLE 3G (ON)
this should then work if not take the iphone into your supplier