you will need:
a usb cable
a sharp craft knife
i would upload screenshots but my computer isn't copying off my "windows phone"
Step 1: Jailbreak and install teh theme
for ios 5.1.1 you need absinthe-win-2.0.1 which you can get by googleing it, it will come as a zip folder.
1 unzip the app
2 run the exe in the folder, that will make another folder inside that on with another exe, run that while your iphone is plugged in and click jailbreak, the app will do the rest
3 in cydia download dreamboard and download os7(if below ios5) if your above ios 5, download os7;revive, DON'T OPEN IT OR IT WON'T WORK. reboot then open dreamboard and choose os7.
os7 revive has more features, eg wallpapers, lock screen, different coloured tiles