Once you have the appropriate keywords to best describe your product or service and are words that people are actually using, you now need to create or modify your content to reflect these keywords.
Let's step back for a second and think about Google and the other search engines. How do they actually know what your website is about? No more and no less than by the "words" on the page. The search engines are not humans; they cannot infer and deduce what your website when they crawl your website. Thus the search engines know what your website is about by the words you use in your content. Of course the search engines have some intelligence and you can't get by with keyword stuffing, but in very basic terms, this is how the search engines know what your website is about.