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On Poloniex, the account name is your username, i.e. justoneartist (or complexring ;)). You don't need to put anything in the memo field.

Do you know if it's the same on Bittrex? I also have a couple of other questions if you don't mind... Basically, would Steem Dollars earn interest on it's own just by holding it in your Steemit wallet, or any exchange? https://steemit.com/steemit/@ynotplay/question-how-do-you-transfer-steem-dollars-from-an-exchange-to-your-steem-account

Analysis is the same. You earn interest in your wallet, not on an exchange.