i keep getting the message to approve a new iphone to continue using icloud i need to log into another device and approve - where is that feature?

Possibly related to -- Get help with iCloud Keychain - Apple Support.

If you can't get approval from your other Apple devices or enter the iCloud Security Code, please follow the steps below to reset your iCloud Keychain.

(For more information please visit Get help using iCloud Keychain - Apple Support)

On your iPhone, iPad, or iPod touch with iOS 8 or later:

1. Tap Settings > iCloud > Keychain > Advanced.
2. Tap Approve with Security Code.
3. When asked to enter your iCloud Security Code, tap Forgot Code.
4. Tap Reset iCloud Keychain to replace your iCloud Keychain in the cloud with the iCloud Keychain items on your device.
5. Tap Reset to confirm. You'll be asked to create a new iCloud Security Code.

On your Mac:

1. Choose Apple menu > System Preferences. Click iCloud, then select Keychain.
2. When asked to enter your iCloud Security Code, click Forgot Code.
3. Click Reset Keychain to replace your iCloud Keychain in the cloud with the iCloud Keychain items on your Mac.
4. Click Reset to confirm. You'll be asked to create a new iCloud Security Code.

Apple ID - Get a verification code and sign in with two-factor authentication