creating clients FB app

I am using this plugin on a clients website that is still under development and not in it’s own domain yet. I built a FB APP on my FB account to test with and got it working OK. Now I want to build the APP for my client and I am an administrator but I cannot find the Create App on my clients FB pages. I am confused, most of the information with a google search is dated 2010,2009, maybe 20011 and none of the screens shown look like what FB does today. Can you provide me a lik to up todate information on what I am trying to do?

Thanks for any guidance.