It takes a few steps but here's what I do.
Have an account on Poloniex.
Transfer your Steem or SBD to Poloniex from the Steemit website. (Go to wallet, select transfer, recipient is poloniex (DONT MISTYPE THIS), and in Memo, put your wallet address)
You can find your wallet address on Poloniex by going to "Deposits and Withdrawals", scroll down to the coin you are transferring, then copy the string of numbers and letters for that wallet. That is your address to receive.
Once you've transferred it over, it'll take around an hour or two to pop into your poloniex account. Then you sell the steem or SBD for BTC.
Create a coinbase account , get verified, connect your bank account to it.
Then send your the BTC from your Steem sale on poloniex OVER to coinbase, and transfer it into your bank account.
:)