The hardest part by far for submitting a sitemap to Google is the creation of the XML file that fits Protocol 0.9. This is made much easier if there is a sample sitemap to refer to.
My latest article is all about exactly how to submit a sitemap with a sample sitemap to make life easier. I have added a few instructions on how to go about making the submission so you are pretty much there.
Go take a look and see how easy it can be.