How do I add a facebook/twitter app?

I have decided not to use the membership plugin because the PPV would definitely cater to my needs. However, I have no idea how to create a FB or Twitter app and I can’t find any information on how to create them. I have looked over the usage page and even without the subscription option turned on I still cannot get the plugin to show up on a post or a page.

Is there a more detailed, step by step installation guide? I am a beginner and I really want to learn this and get it right.