I'll post my finding for everyone to see, with the help of kandrews and a bit of google-fu I figured this out. You need to put a function into your functions.php file.
function my_query_post_type($query) {
if ( is_category() && false == $query->query_vars['suppress_filters'] )
$query->set( 'post_type', array( 'post', 'video', 'attachment', 'rsjp_job_postings' ) );
return $query;
}
add_filter('pre_get_posts', 'my_query_post_type');
WordPress doesn't allow custom post types by default in its posts query. Where you see array( 'post', 'video', 'attachment', 'rsjp_job_postings' ) ); you can add or remove any custom post types that you don't want to show.
I only wanted mine to show up underneath the categories listing so I could have a different page for each category of jobs. So I have this line: if ( is_category() you might need to change that a little to get what you want.
I can now use http://www.mywebsite.net/category/catname/
will only show jobs that are marked underneath the category "catname".