An exchange wallet is basically a website where you can buy, sell, send and receive Bitcoin or other cryptocurrencies.
A few examples are Coinbase, Coinmama and CEX.
To use cryptocurrency to fund your BookMaker account, the first step is to buy bitcoin/cryptocurrency through one of these exchange sites.
Just set up and verify an account, use your credit card or bank transfer to buy Bitcoin, then deposit the Bitcoin at BookMaker. The Cashier will automatically convert the Bitcoin to fiat currency (i.e., US Dollars) to be used in your account.
For a complete guide on the different exchange wallets available, check the main Bitcoin page HERE.