How to create Config Client for microservice architecture?

Question

Java

For the first time I am doing a Spring cloud Config Client, rummaged through several articles and looked at a couple of tutorials using the example of a primitive server-client pair. I understand the purpose of the config, but I got confused in this implementation, I need help.
Given: ready server A, it has several values ​​and the path to the database in the application.properties file.
Now I have created a new Config Client server, and in its application.properties file I should write spring.application.name= - that is, the name of server A?
but how does the Config Client understand at startup which file it should receive from A? Or do I need to rename A's application.properties file to something unique?
Sorry if the question is stupid, but it's very important for me to grasp the logic.