A simple way to do it that will take a few days is converting your SBD to Steem. You can do this within Steemit via your wallet. From there it is a coin exchange with ShapeShift. 

The faster way that is a bit more complicated is to sell your SBD on an exchange. Here is a link explaining how to do that on Poloniex:   https://steemit.com/poloniex/@contentjunkie/how-to-transfer-steem-backed-dollars-to-your-poloniex-account-and-sell-them-on-the-open-market