There is no way to add your crypto currency to your bank balance. This is because your currency whether Dollar, Pound or Euro are regulated currencies and are available in the form of bills or coins. Whereas, cryptocurriencies are non regulated by government or federal banks and don't have any physical form.
Cyrptocurrencies are purely based on virtual coding and are decentralized in nature. The technology that goes behind cryptocurrency and it's transactions is blockchain.
Blockchain is a method where every peer to peer transaction is recorded right from the first transaction to the last reciever. Every peer has a record of the complete history of all transactions and thus of the balance of every account. Once recorded it is not possible to alter the transaction records ensuring no risk of fraud or manipulation.