Submitting your site to search engines is the first step in getting them indexed. The search engines do not guarantee a listing by using their submission forms, so it is always a very good idea to get as many inbound links to your site as possible to futher increase the likelyhood of your site being indexed.
Yahoo! and google supply search results to other popular searches like AOL and MSN, and these 4 engines account for the majority of traffic you will see from all of the search engines out there.
To get your site listed on google, go to http://google.com and type in:
"add my site to google" and the first link that appears on the page should be:
http://www.google.com/addurl.html type your domain in the box with any comments you may have.
For Yahoo! it is not as easy, but non-the-less just as simple, and it is still free.
Go to yahoo.com and do any seach you want, even try the one you are after:
"add my site to yahoo"
Chances are they will not appear as the first, and perhaps not any link on the 1st page of results, at least at the time of this writing.
If you do not see a url to yahoo's submission page, scroll all the way to the bottom of the page and you should see a link to:
"submit your site" in small letters. Click on that and follow the instructions for the free submission option.
Another method is to pay a service to do this for you. One that comes to mind is the one that http://InstaPro.net offers with their traffic blazer program. It runs about $30.00 per year and submits to these engines above as well as guaranteed inclusion in Alta Vista and about 200 other directory submissions, which will save you a lot of time.
Remember if you are not indexed you are loosing out on valuable free traffic and your site may never be found, no matter how good your product or service may be. Focus on content-rich pages with lots of descriptive words and you will be on the right path.
Good luck!