How to enter a URL into a smartphone without doing a search?
These days, browsers on mobile devices, use one bar for searching with an search engine and inserting a specific URL request of web site. 
What you need to do is simple tell them "Touch top bar/address bar and insert this specific URL" or "Insert this URL in the bar and send".
You need to know that if the inserted text is a correctly formatted URL (protocol://domainOrIPAddress:port/path/filename) then the browser will show you directly the web page, otherwise it will use the default search engine for retrieving a possible list of sites that you maybe want to see for the inserted keyword.

In summary, you don't need something special, everything should work without you doing anything on browser settings. However I think there is an option to deactivate the bar for searching cases and only use it for inserting URL, but it's more convenient how it works normally, so by default is one bar for searching and URL request in all browsers.

However, for not letting search engines look on your search/request you need to uncheck some settings on browsers like "Suggestions by Search Engine/Bookmarks".