Saving Details after authentication

for FB & Twitter there is OAuth authentication that is being used. You can refer steps below:
http://www.codeproject.com/Articles/380635/Csharp-Application-Integration-with-Facebook-Twitt

Summary:
Register your app with FB
Use FB dll in your code
pass username & password and you're done

are you able to get details of these users, if yes, then storing is very simple

please share your code for refernce