Before you configure a connection, create an API user and associate it with an API role to grant access permissions for the Marketo REST APIs. You also need to get the client ID, client secret, and REST API URL from your Marketo account to generate an access to authenticate the Marketo custom service.
For more information on how to create an API user and generate the client ID and client secret, see
Custom Services in the Marketo documentation.
The following video shows you how to get the information you need: