How to include a query to the API Gateway?

The question is not clear. Can you please provide some details on what you are trying to achieve?

If you are trying to test the highlighted GET method then you can click on the TEST button to test your API

If you want to understand how to add query parameters or validate or transform the request or response payloads, there are some good tutorials I would recommend that you go through - https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-rest-tutorials.html