Server Action API Authorization Help

I am trying to connect to an API that has a name and a transaction key and can not figure out how to put those in the Server Action API Action.

The authorization credentials work both on the API producer website and in Postman.

postman authorize net.PNG429×720 14.5 KB

The following is the sandbox account so nothing can be done with it, except retrieve the sample info provided by the producer of the API.

API Endpoint: https://apitest.authorize.net/xml/v1/request.api
Method: POST

Code provided:

{
"authenticateTestRequest": {
    "merchantAuthentication": {
        "name": "8aW2aYs7g",
        "transactionKey": "582q9B5EfVtyYT4u"  
        }
    }
}

I would appreciate any assistance that could be provided.