iCloud stores all your crucial data and settings over cloud server so that if you reset your iPhone, all settings and data can be retrieve easily. However, if find my iPhone is on your device then you cannot sign out from iCloud. By going through this instructional page, you will be able to sign out from iCloud if find my iPhone is on your device.
Note: Find my iPhone password is the same password which is configured on the device.
Step 1: Your Apple ID is account that you use to purchase apple services like shopping on iTunes Store, signing in to iCloud, buying an app, using I Message, etc. It is recommend that you use the same Apple ID for all apple services.
Step 2: If you want to sign out from iCloud completely then you need to change email address associated with your Apple ID. Sign in to My Apple ID to change your email address and follow the steps given.
Hopefully, these steps are useful for you. If not or you need further assistance then get in touch with tech team for more support through our toll free number 1-855-602-7997.