If you need to add HTTP Request sampler with dynamic URL that can be different each time from testing to testing you must use one of the Post-Processors offered by JMeter. I usually use Regular Expression Extractor for this purposes.
So, let's imaging that you have "Popular News" web page which contains the links to "News Story" web pages that contains the full texts of news and you want to write a test which will include both "News" page and random "News Story" page.
For this you must include "News" page HTTP Request sampler inside Simple Controller with a Regular Expression Extractor to store random "News Story" page URL to a variable:
Then use the variable with the stored random "News Story" page URL in "News Story" HTTP sampler: