There's a good description of how to insert them at:
http://www.precisionweb.net/front-page-meta-tags.htm
One thing to keep in mind though, keyword meta tags are now largely ignored.
The only search engine I've heard of that does pay attention, though very
mild attention, to them is Yahoo. The search engine companies have vastly
improved algorithms that are used for indexing content and now look for many
things to ensure that a page is valid and not a bunk advertisement. Google
ignores the keyword meta tag completely as it focuses more on who links to
you and the quality of those sites that are linking to you. Don't expect
fantastic results from keyword meta tags, if at all. If you do see results,
don't expect to see them soon, I've heard stories where even with an SEO
company working for them constantly it can take 6 months for a site to show
up in relevant searches.