How to add query variables to WP URL

gistfile1.txt

// create your variable, add your "key" called event_event, and define what the value should be 
//for front end 
$edit_post = add_query_arg( 'edit_event', $user_post->ID, site_url('/edit-events/')  );


//for admin 
$edit_post = add_query_arg( 'edit_event', $user_post->ID, admin_url('admin.php?page=example')  );

// then simply do this for your link 
<a href="<?php echo $edit_post; ?>" title="edit event"><?php echo $user_post->post_title; ?></a>

// then get the value to create whatever query you want
$passed_id = $_GET['edit_event']