It's a complicated process right now that requires a few steps:
- Transfering STEEM and/or SBD (Steem Dollars) to an Altcoin Exchange like Poloniex or Bittrex.
- Use the Altcoin Exchange to convert STEEM/SBD to BTC
- Setup an account on a BTC/FIAT exchange (like Coinbase or one within your country) and link it to your bank account.
- Transfer BTC from Bittrex/Poloniex to a BTC/FIAT exchange
- Use BTC/FIAT exchange to sell the BTC and then transfer the funds into your bank account
Steps 3-5 can be ignored if you just want to hold Bitcoin, which can be used to shop online many places (like overstock, newegg, or digital gift cards from gyft).
It's a lot better than it was a few years ago... but it's all still a bit of a pain.