How do I log out of the iCloud if my phone is unrepairable

Hi there, Dwilliamson84!
Thanks for reaching out to the Apple Support Communities! That is a great question you have about signing out of iCloud of your device that is not turning on and I’m happy to help! Signing out of the old device is not needed to be able to sign in on the new device, so you should be able to sign in without any issues.
Please reach back out if you have any other issues and have a great day!

Is this on a new device? Do you already have an email account added under Settings, Accounts and Passwords?