Right sidebar for twenty thirteen theme??

Hi,

I’m new and am just learning WordPress. I lave a development site at localhost and am trying to add a right sidebar to the twenty thirteen theme. I’ve created a child style.css but am not sure where to go from here. I’ve done quite a bit of searching but have not found a solution to this specific question.

Is it that the core theme can’t be easily modified to make this change?

Thanks in advance,
Mike