As even the newest users to Windows 8 will quickly discover, Microsoft’s newest operating system offers a choice of account types that you can use to log in. A local account works like a typical user account from an older version of Windows, while a Microsoft account offers a bunch of new and useful features that help you get more from Windows 8. Many users, unlearned in the details of each account type may simply opt for a local account because it's more familiar. Those users, after learning what they're missing, will likely want to upgrade.
If you're one of those users and you want to switch from your local account to a Microsoft account, read on for step-by-step instructions to make it happen.
NOTE: If you're more interested in learning about which account is best for you, please check out Introducing Windows 8: Should You Use a Local Account or a Microsoft Account?, which details the features of local and Microsoft accounts.
Launch the Microsoft Account Wizard
First, log in with your local account. Then, open PC Settings and go to the Users section.

Under the Your account section, click or tap the button named Switch to a Microsoft account.

Enter your current password in the space provided and click or tap "Next."

Use an Email Already Linked to a Microsoft Account
If you already have a Microsoft account, formerly known as a Windows Live ID, this process will take only seconds. Simply enter the email address associated with your existing account and click or tap "Next." If you aren’t sure whether or not you have an account, have a look at this article, for more information: Simple Questions: What is a Windows Live ID or a Microsoft account?.

Enter the password for your Microsoft account and click or tap "Next."

That’s all there is to it. Click or tap "Finish" and, the next time you log in, use your Microsoft account information instead of your local account.

Switch Without an Existing Microsoft Account
As you’ve already seen, switching is a breeze if you have an account. If you don’t have a Microsoft account, you can create one. It just takes a bit more effort. To start things off, enter your email address in the space provided and click "Next."

Next, you’ll have to provide information for your Microsoft account. Enter the password, name and location and click or tap "Next."

Next, you’ll need to enter your date of birth and gender. Don’t forget to clear the checkbox if you don’t want to get promotional emails from Microsoft. Click or tap "Next."

You now have to prove you aren’t a robot by entering the distorted text you see in the window. If you’re having trouble making out the characters, click or tap "New" for a different picture or "Audio" for an audio captcha. Be warned however, the audio captchas are extremely difficult to make out. Once finished, click or tap "Next."

That’s all there is to it. You can now log out and log back in using your new Microsoft account.
Conclusion
Now that you’ve switched to a Microsoft account you’ll be able to enjoy new features such as installing apps from the Windows Store and syncing account settings between computers. Also, the various apps that came packaged with Windows 8 including SkyDrive, Music and others will become fully functional.
While using a Microsoft account has a lot of advantages over a local account, there are some concerns about the security of using an email address to log in. Mainly, what happens if someone hijacks your email account? Do you feel the added risk is worth it for the new features offered? Leave your opinions and questions below.
Related articles:
How to Create a New User Account in Windows 8
How to Switch to a Local Account from a Microsoft Account in Windows 8
Log on Automatically to Windows 7 & Windows 8 Without Typing Your Password