TERN trades on a number of active exchanges including all of the Stellar Decentralized exchanges like StellarX, StellarTerm, and StellarPort as well as non stellar exchanges like ExRates. You may also withdraw funds to a wallet, such as a Lobstr wallet, and then proceed to convert/transfer your funds from there to wherever you wish. You should be able to use any of these to withdraw to and convert your funds to USD.   There is a 24 hour processing period for withdrawals before they are transacted.  If you run into trouble or have any difficulties, the support staff for the exchange or wallet provider should be able to help you.