You can withdraw TERN from your account at any time by submitting a withdrawal request through your account dashboard. On the main page of your dashboard there is a button "withdraw" in the card section that will guide you through the process. BlockCard withdrawals generally happen quickly after your request has been initiated, security verified, and approved (pending ➩ approved ➩ completed). Please note that there is a 24 hour hold on withdrawals for security purposes before they are approved, and once approved they will usually complete within a few hours at most depending on the level of congestion that the asset network is facing at that time.
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 transfer from there to wherever you wish. Please make sure that the destination wallet or exchange account is properly set up to receive TERN, including an established trustline if required. For more information, contact support for the specific wallet or exchange.