How to implement adding a link to the source when copying text from the site?

Question

HTML

Please tell me how to add a link to the original page when copying text from this page. I read it on the Internet, but for some reason, adding a link does not work for me using those methods, maybe I inserted it wrong or in the wrong place.
I am not a coder, I will be grateful for a detailed description of what and in which file / files to insert, etc.

Answer 1

Like this, https://jsfiddle.net/yoowordpress/839jnwsf/ add to any included js file
add to