Hi Lori,
These are two related but slightly different issues. The localization steps outlined in the following guide pertain to Apple’s localization, i.e. how the label below the app icon appears on the device:
http://docs.coronalabs.com/guide/distribution/localization/index.html
But within your app, that is entirely your task. Yes, if you want the app to be fully in Spanish as well as English, you’ll need to build that functionality yourself, for example, allow the user to select a language somewhere within a settings scene, and then use that setting to make sure that text, buttons, etc. are all displayed in the selected language. That could be a lot of effort on your part, so my advice is, be fairly certain that you need to specifically target that language demographic before undertaking that task.
Best regards,
Brent