Go to "wallet" and you can claim the rewards there. You should have SOME level of crypto knowledge before using Steemit. A wallet is a personal address much like a P.O. Box at the post office. People can send you money directly to your wallet and you can do the same back. You can also send money to you other wallets, such as an exchange like Poloniex or w/e. There you can sell the currency for FIAT.