Before you can sell any of your earned Steem Dollars you need to have a bitcoin address.
You can get a bitcoin address on a bitcoin web wallet provider such as coinbase or you can open an account with Kraken or Bitstamp or other crypto currency exchanges. It depends on the country of residence which bitcoin wallet provider you can use.
Once you have your bitcoin address you can follow these steps below.
First go to the website blocktrades.us
Select from the left drop down menu (see picture above) the menu item Steem Dollar (see picture below).
You then select from the right drop down menu the menu item Bitcoin (see next two pictures).
You enter the amount of Steem Dollar SBD you want to exchange into BTC (Bitcoin). Then in the next step you need to enter your bitcoin address.
Once you click on the button “Get Deposit Address” you will see below information.
You need to highlight the memo number with your mouse.
Then use the keys Ctrl+C to copy the number.
Go back to your wallet in your steemit profile.
Click on the arrow next to your Steem Dollar amount. From the drop down menu select the item Transfer.
Enter the amount of steem dolars you want to sell and click the button Transfer.
You need to authenticate yourself for this transaction with your username and your steemit password. In the final step click on the Sign Button.
The Steem Dollars will be exchanged on blocktrade.us into Bitcoin and then transferred to your bitcoin address. This can take some time. Most transactions will complete within 1 hour some can take longer. Usually it is around 30 minutes.
I hope I was helpful