First you must verify you are the owner of your Publican site. Click the Add A Site button.
A dialog box is displayed for you to Add a site with. Enter the URL of your Publican site in the text entry field and click Continue.
Follow the instructions that display and upload the HTML file that Google provides to the document root of your website.
When you have confirmed that the provided HTML file has been uploaded to the required location by accessing it in a web browser, click the Verify button.
When you have successfully verified the ownership of your Publican website to Google, return to the Webmaster Tools home page. Your Publican site is listed. Click on it.
You are taken to the Webmaster Tools configuration page for your Publican site. On the left side of the page there is a menu. Click on the Site configuration menu entry to expand it. Its expanded contents includes a Sitemaps entry. Click it.
You are taken to a Sitemap submission page. Click the Submit a Sitemap button.
A text entry field displays, including the base URL of your Publican site, with room to enter the URL of your Sitemap XML file. Enter its location and click the Submit Sitemap button. The details of the Sitemap are displayed in a table.