Debugging Unreal Engine source code

Hi, could you please tell how I can debug Unreal Engine source code? I want to set a breakpoint where it starts importing .fbx models and step through the code as I have some bugs in fbx imports from time to time and want to understand where it fails. Could you please go in some details because at my current level of knowledge I have no idea how to even approach it. I tried setting break points in the code but engine ignores them