general relativity - Curvature gravity and a falling apple?

I know very little of physics after Einstein.

I am aware of that Einstein's gravity theory says that the existence of matters creates curvature of a space-time, so that our Earth orbits our Sun. I can grasp this idea.

But I do not see how to use the language of general relativity theory to justify why an apple can fall?

Answer

I don't have time to write this up properly, but I was asked to make this an answer. (I also feel that John Rennie is about to post something much better)

The key point is that it's not space that's curved, it's spacetime. The apple falls because the accelerating downward path through spacetime is the geodesic through curved space, rather than the "straight" hovering path through spacetime.