If I was a smooth sales man, I would tell you that you can set up the plugin and your Facebook application ID and secret in just 20 minutes. But, i'm not, because if you have ants in your pants like me, and you don't read the directions thoroughly and go step by step, it'll end up taking about an hour and a half.
With that said, I did create this step by step tutorial on how to setup the Download via Facebook along with obtaining your Facebook application ID and secret. If you go through it step by step, depending on your skill level, you'll get it all set up in under an hour. The link to the tutorial is below: