How to find the correct code responsible for a specific functionality

Hello, I really need some help. I am trying to test the Viewing Reference Information functionality of the

I really need some help. I am trying to test the Viewing Reference Information functionality of the Intellij IDEA, and I downloaded the Intellij code from git, but I don't have any experience in this before and I don't know how to find the specific code responsible for this functionality. Please help !Thanks a lot!

Thanks a lot!