I am trying to unlock a phone that I have brought that is originally locked to orange, I have an email from orange with all the instructions but I cannot find my phone when I go into itunes, help!!!!

I have recently brought an iPhone from a friend that is locked to orange network, I have an email from them explaining how to unlock the phone:-

Connect to iTunes using USB

Use the 'restore' option within iTunes (located at the bottom of iTunes not the top)

I cannot find the restore option, having been trying for about 3 hours now, someone please help!!!!!!