Need help with removing iCloud from your device?
You're in the right place.

What is iCloud?

iCloud is Apple's cloud storage service that stores data and pushes it all of your Apple devices.
Starting in iOS7, Apple introduced Activation Lock, which prevents your phone from being activated without the password of the iCloud account on the device.

We are unable to accept any devices that still have an iCloud account on them or are activation locked.

How do I remove my iCloud account from my device?

From the device :
Step 1: Go into Settings
Step 2: Select iCloud
Step 3: Tap to turn off Find My iPhone (or Find My Device)

From iCloud.com :
Step 1: Turn off the device (skip if you've already sent in your device)
Step 2: Log into icloud.com with your Apple ID and password
Step 3: Select Settings
Step 4: Click on All Devices, and choose the device that you're sending in
Step 5: Select Remove From Account