– 1) First create a custom IPSW using the IPSW Builder.
– 2) Click “Ipwner” and browse for the custom IPSW that you just created. This will pwn itunes and allow you to flash custom IPSW files via DFU mode
– 3) Once you have pwned Itunes, put your phone into DFU mode.
– 4) Once you are in DFU mode Itunes will pop up and then you can hold shift and click restore and browse to your custom IPSW file.