Yes, you can use your existing TeamViewer account for TeamViewer IoT.
The account is needed to log into the TeamViewer IoT dashboard to add devices, define sensor monitoring, see triggered alerts and remotely access a device. Your TeamViewer account is basically used to identify you for all IoT services.
To access your account data, go to https://teamviewer-iot.com and log in with your account credentials. On the dashboard, you have access to your devices and defined metrics and can change your account settings.