To sign out of iCloud on your device, go to the Settings application and scroll down until you see “iCloud”. Clicking on this item will bring you to your iCloud settings.
From here, scroll down and make sure that “Find My iPhone” is turned off. Once this is completed, find the red “Sign Out” button at the bottom of the iCloud settings screen.
You’ll be prompted for your Apple ID password to confirm— after that, you’re done!
Removing the phone from your iCloud account will also remove it from the Apple Support site.