1. Log in your Google AdSense account. Go to Tax Information under My Account.
2. Just click the Submit Tax Information button. And it will lead you into:

3. On the next page, there are questions and answer those as NO and click the Continue >> button.

4. Next, you will see a page entitled Certification of No U.S. Activities.. Type in your full name in the text box on the page and click the Submit information button.

That's it! Done.