How do I add a custom field to a sidebar?

I would like to be able to have unique pictures in the sidebar of several pages on my site.

I have discovered that I could possible use custom fields to do this. I have read that I can add code to the sidebar php (in my case I am using a child theme of Travelify and wish to add the custom field to sidebar-right.php)

The code I found is:

<?php
global $wp_query;
$postid = $wp_query->post->ID;
echo get_post_meta($postid, 'customField', true);
?>

Further investigation told me that I should modify ‘customField’ to something more meaningful, so I chose ‘pageImage’. I added this to the end of the sidebar-right.php code.

On my page, I added the new custom field: “pageImage” and gave it a value of the URL of the required image stored in my media.

On viewing the page, in the place of the sidebar is the URL of the image. I feel like I’m halfway there, but need some expertise to complete the task!

This is what my sidebar-right.php looks like:

<?php
/**
 * Displays the right sidebar of the theme.
 *
 */
?>

<?php
	/**
	 * travelify_before_right_sidebar
	 */
	do_action( 'travelify_before_right_sidebar' );
?>

<?php
	/**
	 * travelify_right_sidebar hook
	 *
	 * HOOKED_FUNCTION_NAME PRIORITY
	 *
	 * travelify_display_right_sidebar 10
	 */
	do_action( 'travelify_right_sidebar' );
?>

<?php
	/**
	 * travelify_after_right_sidebar
	 */
	do_action( 'travelify_after_right_sidebar' );
?>

<?php
global $wp_query;
$postid = $wp_query->post->ID;
echo get_post_meta($postid, 'pageImage', true);
?>

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