How would I adapt my code to accomodate a file upload from my form?

Here's my code

Code JavaScript:
<script type="text/JavaScript">
	/* attach a submit handler to the form */
		/* stop form from submitting normally */
		/* get some values from elements on the page: */
		var $form = $(this),
			AddEvent = $form.find('input[name="addevent"]').val(),
			EntryType = $form.find('select[name="entry_type"]').val(),
			Title = $form.find('input[name="title"]').val(),
			ThisDate = $form.find('input[name="date"]').val(),
			City = $form.find('input[name="city"]').val(),
			Postcode = $form.find('input[name="postcode"]').val(),
			JobRef = $form.find('input[name="job_reference"]').val(),
			StartDate = $form.find('input[name="start_date"]').val(),
			EndDate = $form.find('input[name="end_date"]').val(),
			Rate = $form.find('input[name="rate"]').val(),
			Employer = $form.find('input[name="employer"]').val(),
			Notes = $form.find('textarea[name="notes"]').val(),
			url = $form.attr('action');
		/* Send the data using post and put the results in a div */
		$.post(url, { 
			add_event: AddEvent, 
			entry_type: EntryType,
			title: Title,
			date: ThisDate,
			city: City,
			postcode: Postcode,
			job_reference: JobRef,
			start_date: StartDate,
			end_date: EndDate,
			rate: Rate,
			employer: Employer,
			notes: Notes,
			dataType: 'json'
		  function(data) {