Required Fields?

I need to make the e-mail and address fields required but I’m haveing trouble can anyone help.

<?php
$Type = $_POST['Type'];
$First_Name = $_POST['First_Name'];
$Last_Name = $_POST['Last_Name'];
$Company = $_POST['Company'];
$Address = $_POST['Address'];
$City = $_POST['City'];
$State = $_POST['State'];
$Zip = $_POST['Zip'];
$Phone = $_POST['Phone'];
$Email = $_POST['Email'];
$Ports_of_Interest = $_POST['Ports_of_Interest'];
$Collector_Level = $_POST['Collector_Level'];
$Collector_Type = $_POST['Collector_Type'];
$Designer_Specialty = $_POST['Designer_Specialty'];
$Designer_Preferences = $_POST['Designer_Preferences'];
$Designer_Visit_with_Client = $_POST['Designer_Visit_with_Client'];
$Designer_Preview = $_POST['Designer_Preview'];
$Designer_Name_to_Dealers = $_POST['Designer_Name_to_Dealers'];
$Consultant_Specialty = $_POST['Consultant_Specialty'];
$Consultant_Type = $_POST['Consultant_Type'];
$Gallery_Specialty = $_POST['Gallery_Specialty'];
$Gallery_Handle = $_POST['Gallery_Handle'];
$Gallery_Fairs = $_POST['Dealer_Fairs'];
$Gallery_Other = $_POST['Dealer_Other'];
$Dealer_Type = $_POST['Dealer_Type'];
$Dealer_Fairs = $_POST['Dealer_Fairs'];
$Dealer_Other = $_POST['Dealer_Other'];
$Curator_Title = $_POST['Curator_Title'];
$Press_Title = $_POST['Press_Title'];
$Press_Media_Type = $_POST['Press_Media_Type'];
$link = mysql_connect( 'XXXXXXXXXXXX', 'XXXXXX', 'XXXX' ) or die( mysql_error() );
mysql_select_db( 'XXXXXX', $link ) or die( mysql_error() );

$result = mysql_query( "INSERT INTO Invitation_Request (Type, First_Name, Last_Name, Company, Address, City, State, Zip, Phone, Email, Ports_of_Interest, Collector_Level, Collector_Type, Designer_Specialty, Designer_Preferences, Designer_Visit_with_Client, Designer_Preview, Designer_Name_to_Dealers,Consultant_Specialty, Consultant_Type, Gallery_Specialty, Gallery_Handle, Gallery_Fairs, Gallery_Other, Dealer_Type, Dealer_Fairs, Dealer_Other, Curator_Title, Press_Title, Press_Media_Type, Artist_Affiliation) VALUES ( '$Type','$First_Name','$Last_Name','$Company','$Address','$City','$State','$Zip','$Phone','$Email','$Ports_of_Interest','$Collector_Level','$Collector_Type','$Designer_Specialty','$Designer_Preferences','$Designer_Visit_with_Client','$Designer_Preview','$Designer_Name_to_Dealers','$Consultant_Specialty','$Consultant_Type','$Gallery_Specialty','$Gallery_Handle','$Gallery_Fairs','$Gallery_Other','$Dealer_Type','$Dealer_Fairs','$Dealer_Other','$Curator_Title','$Press_Title','$Press_Media_Type','$Artist_Affiliation' )" ) or die( mysql_error() ); 
?>