This template has IdentityServer4 and ASP.NET Core Identity for authentication server and an ASP.NET Core Web API project.
You can visit path '/.well-known/openid-configuration' of the authentication server for a list of all endpoints in the authentication server. More details can be found about the endpoints in the Docs of IdentityServer4.
For using Postman with the API endpoints that require authentication, request a token using postman from the Authentication server.