포스트를 가져오려면 디스커스의 API 키를 어디에 입력해야 하나요?

I’m not sure how you are making your api requests (which tool or programming language), but the api key and username go in the http header.

Here is a curl example from the Discourse REST API Documentation

curl -X POST "http://127.0.0.1:3000/categories" \
-H "Content-Type: multipart/form-data;" \
-H "Api-Key: 714552c6148e1617aeab526d0606184b94a80ec048fc09894ff1a72b740c5f19" \
-H "Api-Username: discourse1" \
-F "name=89853c20-4409-e91a-a8ea-f6cdff96aaaa" \
-F "color=49d9e9" \
-F "text_color=f0fcfd"