To submit your site to Google go here: Webmaster Tools Submit add your website URL and Submit Request.
To submit your website URL to Yahoo you actually need to submit it to Bing as Yahoo search is bowered by Bing now. To submit URL go here: Submit your site to Bing
To submit your website to Bing just follow the link above.
Ask do not accept URL submissions anymore.
Fore smaller search engines like DuckDuckGo, DogPile and so on, there is no need to submit to them as they are powered by Metasearch technology which means they would get their search results mostly form big search engines like Bing and Google.