Nee help with embeding the rocket chat iframe - configuration of rockect chat instance

What I want to achieve:
I wanna have in the right bottom corner of a website a chat icon that will require a name and email from a user. With this information, I created an express API that hooks onto rocket chat API and creates a user, and gives back the credentials. Those I wanna save in the session. Next, I will call my API to deliver the script which will introduce the iframe with the correct credentials. That this will properly work I have to do some configurations within the instance. I did this yesterday night and broke it :smiley:

I am kinda following this guide here Embedding Rocket Chat using iFrame Auth - Mohammed Lakkadshaw's Blog

Here he shows how configures RocketChat

I left out ‘api/v1’ becuas I thought i need to point to my own route, so currently I have
http:// localhost:3000/rocket_chat_iframe
http:// localhost:3000/rocket_chat_auth_get in these two input fields.

I don’t want to screw up the configs again - so How should I configure these input fields?