Create a wallet. Go to blockchain.info and create an online wallet or download a desktop client.
If you use the later, remember to keep the Wallet safe (backup it and encrypt it).
Get Bitcoins. Go up and fill the form. You can do this once an hour. We will transfer the Bitcoins in about a week.
Use them! You can spend the Bitcoins in many ways, buying items, gambling or selling them for common money.