First, you will need to get a Bitcoin wallet. This is where you store your bitcoin for further use. There are basically two types of wallets, online wallets and software wallets.
Online wallet: This kind of wallets are the most comfortable to use but also the most dangerous as you are keeping your Bitcoins on a third party service. You should only use those if you are either in a hurry or dealing with low money quantities. Some nice examples of online wallets are LocalBitcoins and Coinbase.
Getting your online Bitcoin wallet is as easy as signing up on any of the websites listed above and you will get your account details on your mail. You will see your bitcoin wallet address once you log in, it will be something like this: 1F1tAaz5x1HsXTCNlbtMDqcw6o5GNn4xqX. You can use this address to send bitcoins to it and store them in that wallet until you want to make a purchase. Remember to write down your login details and bake a backup of the wallet if you want more security.
Software wallet: This is a more secure version of bitcoin wallets as everything is hosted on your computer. You should normally use this option. Some common software wallets are Electrum and Bitcoin-QT.
Using those is pretty easy, just download and install. The basics are the same as in an online wallet, your new wallet will be created upon the first start of the program. On electrum you should write down your unique seed and on Bitcoin-QT it is recommended to set a password for your new wallet, otherwise your Bitcoins will be unprotected. A list of receiving addresses will be shown to you, you have to use those to fund your wallet.
Next you will need to buy some bitcoins, this is a delicate process because we have to choose the exchange and the payment system depending on your location and possibilities. But please do not be afraid, we will help you. There are lots of ways to get your bitcoins:
Bitcoin ATM's: If you have a Bitcoin ATM near your location wait no more and use this as it is the most secure, fast and anonymous way to get your Bitcoins. Find nearby ATM's at Coin ATM Radar. Using those is very easy, just follow the steps from the display, the ATM will take your cash and convert it to Bitcoins and send them to your wallet.
LocalBitcoins: LocalBitcoins is also a great service where you can trade cash for Bitcoins directly with people. Otherwise you can also buy bitcoins here using Paypal, bank transfers and all sorts of online payments.
Bitcoin exchanges: Using Bitcoin exchange is the most safe and cheap way to buy Bitcoins but it is also the less anonymous, if you happen to buy Bitcoins from an exchange you should later wash your coins before using them. Some examples of exchanges are Kraken and Coinbase.