Steps for installing and setting up your XML sitemap:
Login to your WordPress Admin account.
Click on the Add New link in the left hand column under the Appearance tab.
Search for Google XML Sitemaps.
Click the Install link located in the far right column titled Actions.
A window will pop up asking you to install the plugin. Click Install Now.
On the next page, click Activate Plugin.
Once the plugin has been activated, you need to setup your sitemap. To do so, go to the Settings tab in the left hand column and click the XML-sitemap link.
At the top of the page, you’ll see The sitemap wasn’t built yet. Click here.
Once you click the above link, you should have a new xml sitemap located at http://www.yoursitename.com/sitemap.xml.
Submit sitemap to Google Webmaster
Add Meta tag to wordpress for Google Webmaster Tool Verification