hughy
URL means Uniform Resource Locator a pointer to a resource on the World Wide Web. Or to put it into every day language it its a web address e.g www.passionford.com

The URL that its looking for is similar to https://passionford.com/forum/general-car-related-discussion/286719-how-can-i-give-somebody-a-score.html
and found in your browser at the top of your page....just copy that

So you'd want to have one browser opened on the post that you bought from.
Goto the browser at the top highlight the http.......... bit.
right click on you mouse
Copy.
Go to the field that is looking for the URL
right click on your mouse.
Paste.

That should be you sorted.