Use structs when you have related data that belongs together. Coordinates, dates, RGB colors, student records. If you pass five parameters to every function, you probably need a struct.
Don't use structs for unrelated data. A struct with int age; string cityName; double temperature; makes no sense. Those aren't connected. Structs model entities. Start simple. Define a struct when you see the need.
When you catch yourself managing parallel arrays or long parameter lists, that's your signal.