If you want to download apps from the Windows Store, you’ll need to use a Microsoft account.
Switch a local account to Microsoft Account.
a) Press “Windows + I” to open settings option.
b) Select Change Pc settings.
c) Select User account.
d) On the right side, it will show your current account with a option that says “**Switch to a Microsoft account”.**e) Once you have setup your Microsoft account (this requires a Windows Live ID (Hotmail or MSN, Outlook.com). Enter the new email address and this will change the email address.
For more information on user account, refer to the articles.
Create a user account
http://windows.microsoft.com/en-IN/windows-8/create-user-account
Which user account is right for me?
http://windows.microsoft.com/en-IN/windows-8/which-user-account-for-me
http://windows.microsoft.com/en-IN/windows-8/microsoft-account#1TC=t1
If you have further questions, please do post your query in Microsoft Community. We will be glad to assist you.