Add FirstName in ASPNETUSRES

hi i want to add FirstName column in ASPNETUSERS table using the following tutorial i could not find IdentityModel.cs file inside my project. i am usingweb form project.

http://blogs.msdn.com/b/webdev/archive/2013/10/16/customizing-profile-information-in-asp-net-identity-in-vs-2013-templates.aspx