Google sites maps are a convenient way to submit a collection of links to google. The idea being that this will save google a bit of time searching for links in you HTML document. Though this does not guarantee listing on Google it improves you chances for the same.
Its is a three step process
1) Create a sitemap
2) upload the sitemap to your site
3) Tell google your sitemaps location
Creating a site map is a rather simple
Follow the instructions below to comeplete the sitemap process
Create a Map as mentioned here
The EASY WAY would be to visit the Google sitemap Generator .
Save the resulting files on your machine and upload this VIA FTP or you Web based admin panel.
Once you do this you have completed step one of google sumission / optimzation. You can now start tracking you Page Rank here. If you are doing the right things you page rank will go up. If not it will go down.