Step 1: Click here to go to the Chrome Webstore and get the MetaMask plugin
Step 2: Click "Add to Chrome" to Install MetaMask as Google Chrome extension
Step 3: Click "Add Extension" to confirm and MetaMask will be added
You can see that MetaMask is added by the little fox logo that shows up on the top right corner
Creating a new wallet
Step 1: Click the MetaMask logo
Step 2: Read and agree to the MetaMask's Terms and Conditions
Step 3: Click "Create new vault"
Step 4: Enter a strong password and click "OK"
Step 5: Metamask will now show you your seed. It is very important that you copy and store those 12 words, without them you cannot restore your wallet.
Your account is now created! It's possible that 1 Ether shows up on your balance. That's because you're on the testnet
Changing to the Mainnet
Step 1: Click "Morden Testnet"
Step 2: Select "Main Ethereum Network"
Step 3: MetaMask will now ask you for the password. Type it and click "Unlock"
Step 4: Click the copy logo to get your wallet address. Then all you have to do is send Ether to it from your favorite exchange or wallet.