How to use a plain vanilla get/post method to obtain a authentication token in postman?

Question

I have been building a Duende Identity Server. It is said that the Authorization Code Flow can be performed by visiting the following link It looks like a Get method. I can obtain an Authentication token using the Authorization tab without any issue.

But I just can't get a token for this Get-like request using the plain Get/Post-method. What's different between the Get/Post-method and the "Configure New Token" setting? "Configure New Token" looks like a magic. How to achieve the same result using the Get/Post method?