Great Question. You can get a test Client ID and test data from the Project Console for testing your integration with Visa Checkout in the sandbox. To use Visa Checkout in production, you must apply and be approved for a Visa Checkout Merchant Services account. Contact firstname.lastname@example.org for more information or to begin the production onboarding process.
Please refer to the requirements in implementing Visa Checkout in the below link. Details on Service Activation, working with processor or PSP or creating a relationship with a Visa Checkout partner are detailed in the below link.
Please let me know if you have any further quesitons.