I think very big exchange in the world, and the exchange bittrex have a characteristics friendly to user's like a commision 0,25% and have deposit and withdraw Bittrex deposits and withdrawal transactions are carried out only in cryptocurrencies, as the exchange does not have the possibility to trade with fiat money.
Therefore, to have funds in the account, you must initially buy or send your cryptocurrencies from another platform.
To deposit or withdraw funds to your account, you must go to the Bittrex website under the Wallets tab, select the desired cryptocurrency and send or withdraw your coins.