It is pretty easy if you use a free tool such as SitemapX which can automatically generate and submit a sitemap to main search engines such as Google, Yahoo, MSN, etc. One-minute easy setup, no skill needed. Or you can search one on Google.
Google provides site map generator. ie - xml-sitemaps.com which provide all type of sitemaps like XML, HTML, .TXT n so on. it is very easy and fast.
If you are using Wordpress then there are several good sitemap plugins. If you are not using Wordpress then I would suggest converting your site into a Wordpress site.