Make an account at Coinbase. You can use a referral to buy bitcoin as well, if you do so with coin base both you and your referral will receive an extra $10, so long as you spend $100 or more. You will need to link a credit card or bank account to coinbase, and it's pretty straight forward after that. Just punch in the amount you want to spend and receive an appropriate level of bitcoin, or vice versa, put in a bitcoin amount you want to buy and it'll tell you how much it'll cost. There are limits on coinbase though, for new users. If you wire money directly to coinbase though, you can send quite a bit more than you could if you just link a bank account.