Being that you used the term “Master Page”, I’m going to assume this is an ASP.NET Web Forms project.
Think of a Master Page as an abstract class. You cannot view it directly, but implement it in your pages.
Check out this beginner tutorial
http://www.codeproject.com/Articles/333650/Beginner-s-Tutorial-on-Master-Pages-in-ASP-NET
solved Adding new item in Visual studio 2010 [closed]