The locale I need is not included in the standard Magento language extensions, so I need to create my own.
It will be es-us - Spanish language for the US.
I found this article: http://kb.magenting.com/content/14/50/en/translate-magento-interface-magento-localization-tips.html
It says:
"If there are no localization package for your locale you can create it by simply copying localization directory from English or any other translation."
Can someone walk me through how I get from that quote to having Spanish (USA) in the locale drop-down?
Thank you so much for your help!