If you want use bitcoin you need special bitcoin software.
In the past only one software was available - original bitcoin client from Satoshi Nakomoto. Today's we have great selection of bitcoin clients for all modern desktop and mobile operation systems. Modern software also can support multiple crypto-currencies (altcoins).
If you do not want install any bitcoin software you can also use online bitcoin wallets and other services.
You can choose your preferable bitcoin wallet on the bitcoin.org.