How can u remove an iCloud from an iPhone

You have forgotten your Apple (iCloud) ID?

See if you can recover the ID/password.

Apple ID - How to find your Apple    An iCloud e-mail address is an Apple ID.

Apple ID - Find              

For the Apple ID password, enter the Apple (iCloud) ID and click Forgot Password.

Apple ID - Manage            

Apple ID – Forgot Password            

You can Reset your Passcode of your Apple ID , check out this link as this may be helpful to you :

https://support.apple.com/en-gb/HT201487