This is a step by steb tutorial for creating a facebook app. At first you have to register as a facebook developer in https://developers.facebook.com/ , Then download the dll's FBHelper.dll and NewtoSoft.dll from this link
step:1 Navigate to https://developers.facebook.com/ and click on the app link.
step:2 click on the create new app button
step:3 Enter the app name and name space. name space is simple a name which is used to identify your app.
step 4: Complete the capche.
step:5 You will get a unique app id and app secret code. Sandboxmode should be enabled while creating and testing your app.
step 6: Open your visual studio and create an asp.net website. this is for getting your testing url.
step 7: add new page.
step 8: add the following dll's to your projects. Newtonsoft is not requered unless you are not using the direct FQL method from the FBHelper.
step 10: take your site url by running your website.
step 11: https://developers.facebook.com/ and change your canvase url. this url will be called after the user authenticate your app.
step 12: Customize your permissions.
step 13: add
using FBHelper.Entity; namespaces. then you are ready to go. see the below screen shots