Hi,
If your content contains the words then searching on the words should find it so there is nothing special to having keywords in your content.
You can add meta keywords to any page from the page settings, but the internal search does not know about these words, it only knows about the content, though google search may see the meta key words. Generally its not good to put unrelated key words in your meta settings, they should be related to the actual content.
Hope it helps,
Joe