How can I add a second light to my bathroom circuit?

I am new to the forum and this is my first major project.

I am looking for some help for adding a vanity light above my sink, and wiring it to the existing switch that controls the ceiling light so that both the vanity and ceiling light turn on at the same time.

I know that i need to run some cable and mount the vanity light.

My question is about how to wire the vanity light to the existing outlet/switch receptacle.

thanks