Adsense have a PIN hold before you can withdraw your first earnings. Google will send it to you when you have $10 in your Adsense account. You should recieve it within 30 days. But if you haven't recieved it in that time try following these rules-
1. At first request a reissue of PIN code. You can request upto 3 times for a PIN.
2. If you still didn't recieve PIN for 3 times you can contact Adsense support here.
3. Wait for a few days and let them contact you by email.
4. They will ask you to submit a Phone bill, Bank Statement or other document for verifying your address.
5. Once they verify your document you will recieve your earnings.