To create a new Page with Master Page:
While Add a new Item, A dialog Box will open to give the name to save, there one check box will be there, 'select Master Page', Check that and give ok, and another Dialog Box will open. There you need to select Master Page. & now Master Page will be selected.
To Add the Master Page with Existing Page:
<%@ Page Language="C#" MasterPageFile="Masterpage.master" AutoEventWireup="true"
CodeFile="default.aspx.cs" Title="Untitled Page" %>
This code will be available in the design page of default.aspx, (First Line of the Page)
you should add