Facebook App ID - mine or my clients?

I'm setting up Events+ for a client.

I'd like to enable Facebook and Twitter login for the client - both require an App ID. When I follow the links to the Facebook developer site, or the Twitter dev site they seem to require that I create an app. I don't want to create an app, I simply want to enable that feature of Events+

Is there something I'm not doing correctly?

Also, it seems both the Facebook and Twitter App ID pages assume the developer is the same person as the Facebook / Twitter account holder. Is that right?

If that's the case, I need to ask my client for the Facebook and Twitter login credentials. Is that right?

Thanks for listening.