To activate the hotspot function, you need to install the latest iOS software update.
Once, the software is updated, go to the settings menu.
In the settings menu, you will see the personal hotspot item, tap on it.
Then, on the personal hotspot menu, switch the button to ON and choose a Wifi Password.
That's it ! Go on your computer and scan the wifi networks. You will find the Iphone hotspot refered as the name of your iPhone in iTunes.