You can find your API key under the Integrate tab, which will become available to you once upload your data.
You will have to make a POST request to the URL that you are provided, which should look something like this:
The endpoint will expect a JSON in the payload body and can process requests in curl, python, or node.js. The request must be an object with the data property and a list of the texts you want to classify as values. The response will be JSON formatted, and a successful classification will return a list of results for each given text in the data parameter, with classifications keys for each result.