How do I link a HTTP Response (PUT) for login with a HTTP response (Get), such that credentials are used in the GET

You will need to supply more info if you require help

Copies of the complete messages from the http nodes.
Any error messages.
The Postman info.
Any documentation for the rest api of the switch.

There’s a great page in the docs (Working with messages : Node-RED) that will explain how to use the debug panel to find the right path/value for any data item.

Pay particular attention to the part about the buttons that appear under your mouse pointer when you over hover a debug message property in the sidebar.

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In order to make code readable and usable it is necessary to surround your code with three backticks (also known as a left quote or backquote ```)

``` 
   code goes here 
```

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See this post for more details - How to share code or flow json