Hi there,
The action attribute specifies where to send the form-data when a form is submitted so you need to replace the '#' with your target file. Now, I don't know what you are doing in your PHP file but the global array $_POST will have the value of all of your form inputs fields which can be used in order to process your contact form. For example, in order to get the value of the input field "fullname" you can do something like this
$fullName = $_POST['fullname];
Not to forget to say that you must not trust any inputs and must clean all before using in your script
Hope this is easy to understand