According to the files in the Product Extra Fields plugin, they've added the following lines in the middle of your tpl_product_info_display.php file (assuming you copied the file over to your template, or better yet, assuming you carefully merged its unique changes into your own template):
All of this code takes care of displaying what's in those custom fields:
<?php
if (!TPP_GLOBAL_EXTRA_FIELDS_ON_TAB) {
?>
<?php if (isset($products_file_1_link) || isset($products_file_2_link) || isset($products_file_3_link) || isset($products_file_4_link) || isset($video_file_link) || isset($extra_field) || isset($text_1) ||isset($text_2) || isset($text_3) || isset($text_4)) {
echo '<div class="files"><div class="filesHead">'.TEXT_PRODUCT_MORE_INFO.'</div><ul>';
}?>
<?php if($extra_field!='') {
echo '<li>'.$extra_field . '</li>';
} ?>
<?php if($text_1!='') {
echo '<li>'. PRODUCT_TEXT_1 .' '.$text_1 . '</li>';
} ?>
<?php if($text_2!='') {
echo '<li>'. PRODUCT_TEXT_2 .' '.$text_2 . '</li>';
} ?>
<?php if($text_3!='') {
echo '<li>'. PRODUCT_TEXT_3 .' '.$text_3 . '</li>';
} ?>
<?php if($text_4!='') {
echo '<li>'. PRODUCT_TEXT_4 .' '.$text_4 . '</li>';
} ?>
<?php if(isset($products_video_link)) {
echo '<li>'.$products_video_link . '</li>';
} ?>
<?php if(isset($products_file_1_link)) {
echo '<li>'.$products_file_1_link . '</li>';
} ?>
<?php if(isset($products_file_2_link)) {
echo '<li>'.$products_file_2_link . '</li>';
} ?>
<?php if(isset($products_file_3_link)) {
echo '<li>'.$products_file_3_link. '</li>';
} ?>
<?php if(isset($products_file_4_link)) {
echo '<li>'.$products_file_4_link;
}
if(isset($products_file_1_link) || isset($products_file_2_link) || isset($products_file_3_link) || isset($products_file_4_link) || isset($video_file_link) || isset($extra_field)) {
echo '</ul></div>';
}
?>
<?php
}
?>