Connecting idealo's business API to Funnel is made using a Client ID and a Client Secret. You can generate these in idealo business by accessing "My idealo" → "Shop Settings" → "API Clients" → "Create new API client".
When creating a new API client, make sure to give access to "idealo Business API" (see screenshot).
Note! The Client Secret is only shown once at creation time! If you no longer have access or forgot your Client Secret, please create new credentials to connect with.