How can I add Spanish to my website?

Hi.

How have you been, Lindsey?

To get started with a new language please go to your Dashboard → Languages app.
Here and now, you will be able to click 'Add New Language' button and select Spanish from the list.
I guess you will find this article pretty helpful on your way as it pretty much covers the process step-by-step. 

Warmly,

Ines.