Launch the Test or Production service links in your Chrome browser and enter the credentials. The first line will have the link to the metadata definition.
You can also directly launch the metadata by framing the URL as {Service link}/$metadata
Contact your Project Owner to get the Test or Production service links from the Builder.
Create a new request in Postman. Select GET method from the dropdown and paste the service link from Hubway. Suffix the link with the name of the Entity from which you want to fetch data.