March 21, 2011
If Personal Hotspot feature is not enabled and still missing on your iPhone 4 after upgrading to iOS 4.3 then read this tutorial for possible fixes. However, in case your provider does not allow tethering at all then there is no immediate fix.
February 14, 2011
This guide will show you how to enable and and use Personal Hotspot on iPhone 4. This feature is presently available only on the Verizon iPhone 4(iOS 4.2.6) and GSM iPhone 4′s running iOS 4.3 beta. When iOS 4.3 will be released for everyone it will be available to all iPhones.