The keywords are what we call “tags” in the CMS. You may add a few keyword tags to each page, sermon, post, etc. Every tag you create will be available site-wide. This means after you create the tag once, it will be available to use again on any other content when you click the “Show All Tags” button.
You are able to manage those Tags under: Admin > Tags.
To help your search results you will also want to write a 300+ character description of each page, sermon, post, etc. The Description does not show on the live site but it will show when Google displays the link in search results. In both your Description and Tags be sure to use words you know people are searching for.
To learn more about search engine optimization (SEO), please review the Article “How to improve your Google rank with SEO”, as it goes into great detail about how to strategically optimize your website.