to upload a file, your forms encoding type must be set to "multipart/form-data". change the form tag:
<form action="reEnrollment_Insert.php" method="post" name="WADAInsertForm" id="WADAInsertForm">
to:
<form action="reEnrollment_Insert.php" method="post" enctype="multipart/form-data" name="WADAInsertForm" id="WADAInsertForm">