Depends on what you want to exchange it for. When you want to exchange it for Steem you can do this on the internal market:
https://steemit.com/market
When you want to Exchange it for other Cryptos you could use:
You can move them to the Bitshares platform too. And then trade then there. Which is a bit more complex:
There are other ways, but they are on centralized exchanges which I do not use myself.
RE: Dogecoin did it!