display does not echo, so you need to echo it.
<?php echo $mypod->display( 'my_field' ); ?>
More info and examples at http://staging.pods.io/docs/code/pods/display/
Also you will need to specify an ID of the item you want the field from in the pods() call, like:
<?php $mypod = pods( 'my_pod', $id ); ?>
Or use a find() call to get the record you want. http://staging.pods.io/docs/code/pods/find/