Your Fuse wallet is controlled by your Device Key and 2FA Key (determined by the chosen two-factor authentication method). There are two primary scenarios where you might want to replace your 2FA Key:
If you lost access to your current 2FA Key
You want to switch your 2FA Key from iCloud to a Ledger to upgrade your security.
Here's how to change your 2FA Key:
Navigate to the “Security” tab and click the three-dot button to the right of your 2FA Key.
Select the “Change 2FA Key” button.
Next, choose the wallet you want to connect and find your wallet. Ensure your Bluetooth is turned on and your Ledger device is powered on and unlocked.
Select your cold wallet. Once it appears, click “Next”.
Review your cold wallet’s address as your new 2FA Key and click “Finish”. Your cold wallet will be updated as your new 2FA Key.
Read this article for more information on Fuse's security.