You don't have to change any settings. Just install the custom carrier file, and if successful you'll be able to go into settings>general>network and enable tethering. I then plugged my phone in USB and went to the network settings where your airport etc stuff is. It was listed as Ethernet adaptor 3 or something like that..leave the boxes blank and select configure with DHCP, then apply. Your iPhone will probably crash and restart when plugged in, this happens only once...let me know how it goes.