Checkout number 2 on the installation instruction:
== Installation ==
1. Upload the full directory into your wp-content/plugins directory
2. Make your blog directory writable OR create two files named sitemap.xml and sitemap.xml.gz and make them writable via CHMOD. In most cases, your blog directory is already writable so you don't need to do anything.
3. Double make sure that your blog directory is writable or two writable files named sitemap.xml and sitemap.xml.gz exist!
4. Activate it in the Plugin options
5. Edit or publish a post or click on Rebuild Sitemap on the Sitemap Administration Interface in the menu under Options -> XML Sitemap
|