If you signed in with your Microsoft account when you set up Windows, hooray!
If not, that's OK—you can sign in any time. And if you're not quite sure what a Microsoft account is, we'll tell you.
What it is
Have you ever used Outlook.com, Hotmail, Office 365, OneDrive, Skype, Xbox, or Windows? The email address and password you use for any of those services is your Microsoft account. If not, it's easy to create a free account with your email address or phone number at account.microsoft.com.
Your Microsoft account gives you access to apps and games from Microsoft Store, and lets you see your settings and other stuff across multiple Windows 10 devices. Read more about the benefits of Microsoft account.
How to sign in
Select the Start button, then select Settings > Accounts > Email & app accounts.
Under Accounts used by other apps, select Add a Microsoft account.
Follow the prompts to add your Microsoft account. You may need to verify your identity by entering a confirmation code.
If you find that you're having issues signing in, or if you forgot the password for your Microsoft account, the Microsoft account FAQ has some helpful pointers.