In the Describe your search engine section, type a name and description, and pick the language you want. You can change any of these later by going to the Basics page on the Control Panel.
In the Define your search engine section, add the sites you want to include. You can include any sites you want, not just sites you own. You can include site URLs or page URLs, and you can also get fancy and use URL patterns.
Under Select an edition, click the options you want, agree to the Terms of Service, and clickNext.
Select the style you want.
In the Try your search engine section, test it out. Don't like the results? Go back to the previous page and add (or remove) sites.
To get the code to implement Custom Search on your website, click Next. Copy the code and paste it into your site wherever you want your Custom Search Engine to appear.