To access the GraphQL service, I would use this URL http://localhost:9090/denodo-graphql-service/graphql/<database>, once I start the Virtual DataPort server. By using the above URL you can try accessing it in any of the Apollo server supported GraphQL clients.
You can refer to the [Accessing OData and GraphQL services](https://community.denodo.com/videos/details/Data%20Services/Denodo%208.0/Accessing%20OData%20and%20GraphQL%20services) video tutorial to see the steps to access GraphQL services. Additionally, to configure you can follow the document [Invoke Denodo views using GraphQL service](https://community.denodo.com/tutorials/browse/dataservices/6generic_endpoints) and [Configuration](https://community.denodo.com/docs/html/browse/8.0/en/vdp/administration/restful_architecture/graphql_service/graphql_service_configuration) of Virtual DataPort Administration Guide.
Also, Denodo GraphQL Service can be accessed via various tools like Postman, GraphQL Playground, GraphiQL, etc.
Hope this helps!