Hi! Can you clarify where you want the job description to appear? Is it on the job listings page? If so, then you’d need to override this file:
https://github.com/Automattic/WP-Job-Manager/blob/master/templates/content-job_listing.php
https://wpjobmanager.com/document/template-overrides/
To display the description, you’d have to add code like this where you want it, in the override file:
<?php wpjm_the_job_description(); ?>
You’d also need to style it appropriately, most likely (depending on your theme).