You had to set this withdrawal address yourself. This address should be from your wallet. You can use Freebitco.in as a wallet and shop online and something. But every time when you will want to spend these BTC, you will have to change this address to address which is given by recipient, online shop for example. It's not very convenient, so I suggest to withdraw your BTC from Freebitco.in to your personal wallet and then spend it.