Surprisingly, not too different from a regular search engine. You simply key in your search term into the search engine, and it will return the relevant results.
The reason you can’t simply search for dark web content on search engines like Google while using browsers like Chrome is that they do not have dark net access. As most users of popular search engines don’t use dark net software, popular search engines simply don’t crawl for them.
Specialized dark web search engines are designed to crawl and index dark web content, though sometimes, they also crawl for surface web content.