I'm on Three and it's on Settings then from the top there is Airplane Mode then Wi-Fi and then Personal Hotspot .. it works great (using my ipad to connect) but I just want to know it's not going to cost me a heap of money somehow! lol
It's network based.
I'm on Three with a sim-only deal and tethering/personal hotspot is enabled and part of my 1GB usage. Very fast as well, can't beat Three for 3G coverage and quality. I once used it instead of an ADSL connection as it was quicker!