RDP API through Postman

Using RDP API and would like to use it through Postman. They would like to know how they can import the spec files for the open API for all of RDP? If he can go to a specific endpoint in the playground, select Swagger he can download the individual schematics. In the past, he recalls there was a way to get the spec files for all of RDP. The client was routed to DEV portal but he is still having trouble getting his account to work with Postman. He followed the tutorials on the Dev portal but it seems like that is from an earlier version of postman.