Random link from link manager plugin

Hello,
I want to use this plugin
https://infovore.org/code/wordpress-plugin-get-random-links-from-link-manager/

to show a random link in my sidebar from the links list on wordpress. I followed the instructions but I do not understand how to show the link in sidebar? I am new to php so I did not understand that part of the instructions. Can someone please help me out? What exact coe do I put on the sidebar to show a random link?

Also, I get some php errors on admin pages after activating the plugin in my wordpress…they appear sometimes only…for example, the error showed up right when I activated the plugin but then next time I visited my admin panel it was gone. It also appears everytime I try to edit the theme files in my admin oanel and save them.

The error is this :

Warning: Cannot modify header information - headers already sent by (output started at /home2/bouncyj/public_html/wordpress/wp-content/plugins/get_random_links.php:57) in /home2/bouncyj/public_html/wordpress/wp-admin/theme-editor.php on line 59


I dont understand, please help!