A Google Webmaster tool is free and easy to set up tool. Here I have mention some useful advantages to submit your site to Google Webmaster Tools.
1) Using this tool you can submit your sitemap.xml
2) Generate and analyzing the robots.txt file
3) Improving your inbound Linking Quality Score
4) It provides the Key Diagnostic Data about Your Site
Check out the following steps you need to take to use Google Webmaster tools.
1) Create a Google Account
2) Now, Log in to Google Webmaster tools
3) Add your Website
For more detail, visit the following link.
http://www.squidoo.com/googlewebmastertools