Navigate to the download section of this website and choose the wallet that you would like to start with. The "core" desktop wallets are considered to be the most stable and most secure as they are what is called "full nodes."
The easiest way to acquire your first DigiBytes is to purchase them on an exchange. Two exchanges most people start with are Poloniex.com or Bittrex.com
Typically you will need to use your fiat currency to purchase Bitcoin first and then trade Bitcoin for DigiBytes on the above-mentioned exchanges.
You can begin accepting DigiBytes as payment for any kind of goods or services you sell. All you need to do is download a wallet and send a person paying you a DigiByte address.
You can begin earning DigiBytes by contributing your computing power to a process that is known as mining. Mining is how new DigiBytes enter circulation.