1. Sign up for a Bitcoin Wallet
In order to buy bitcoin, you must first download a bitcoin wallet or sign up for an online bitcoin wallet like Coinbase and create a bitcoin address (ex: 3EfKz5Mo7fvL9byK15527xCiDhxs1bVD25). Your bitcoin address is where bitcoin is sent to and from so it ends up in your wallet.
2. Sign up for a Bitcoin Exchange
Once you have your bitcoin wallet and your bitcoin address you will need to send bitcoin to your address in order to see the funds in your wallet. This step requires whats known as an exchange, and it works just like exchanging money when you travel overseas and need to exchange your home currency for the local currency. As an American, when I travel to Europe, I need to exchange my U.S. dollars for Euros and the same goes for bitcoin. Coinbase is a very popular option because it works as a web based bitcoin wallet as well as an exchange, so you only need one account to manage your wallet and exchange traditional currency for bitcoin.
3. Use a debit card, credit card, or bank transfer to buy bitcoin
Once you have your Bitcoin wallet, you can use traditional currency to buy bitcoin with a variety of payment methods including debit cards, credit cards, and even bank transfers (ACH). The Bitcoins are then transferred to your wallet, and will remain there until you send them to another wallet.