So I think I got somewhere.
I was able to add the filed to my edit-event.php within EM and it displays on the front end.
However when I click on submit event it does not do anything and therefore the event is not saving.
I added:
<?php acf_form_head(); ?>
<?php the_field(‘sponsors’); ?>
<?php acf_form(); ?>
Do I need to add something else to save the field? Or is there is a conflict between ACF and EM when I use this approach?