From the PHP web site:
mail(string to, string subject, string message[, string additional_headers [, string additional_parameters]])
I would suggest making the following variables to make it as clear as possible to read
$to = "someone@somewhere.com";
$subject = "Thank you for your application";
$message = "Welcome to ePN.\nPlease login blah blah\nThank you very much\n\nAdministrator of site";
$from = "From: webmaster@myserver.com\r\n";
mail($to, $subject, $message, $from);
In $message you can use "\n" for a new line, and the php manual page says that you have to use \r\n to seperate headers in the optional headers section. I don't know if it is neccessary when you're sending one header, but I put it in just in case.
HTH
glj