Using ACF to display different widgets on pages

I have setup a custom field for displaying widgets based on different pages and posts.

How can I code this?

Here is the code for the sidebar

<?php /* Widgetized sidebar */
if ( !function_exists(‘dynamic_sidebar’) || !dynamic_sidebar(‘sidebar-9’) ) : ?><?php endif; ?>

Here is the code for the custom field

<?php the_field(‘previous_page’); ?>