i can't turn off find my iPhone screen is broken

1. Sign in to iCloud.com with their Apple ID.
2. Go to Find My iPhone.
3. Click All Devices at the top of the screen.
4. Select the device that you want to remove from iCloud.
5. Click Erase [device]. Select Next until the device is erased. 
6. Click Remove from Account.

Log into your account at iCloud.com/find and remove the device from the list.