How to access correctly with Basic Auth?

[#1]

Where can I add credentials into request to access endpoint by Basic Auth?

To access a data endpoint, I have created a API Gateway.
Now I need to know how to tell apigee to provide authorization as Basic Header in my request?
The endpoint is secured by htaccess.

I have creaded a 'Basic-Authentication-1' and put it into "Proxy Endpoint" Pre Flow and PostFlow als well as into "Target Endpoints" in PreFlow and PostFlow.
But this does not work. I get an error 500.

Moreover, I have deleted 'Basic-Authentication-2' several times, but it still appear again.