From the Start screen, swipe left to display the Apps list. Alternatively, tap All apps (located in the lower-right; may require scrolling).
Tap add an account.
Tap Microsoft account.
From the 'Keep your life in sync' screen, review the information then tap sign in (located in the lower-left).
Enter the appropriate email address and password then tap next.
If presented with a 'Verify your identity' screen, enter a different mobile number to receive a text message containing a security code to be used in the event you ever lose access to the account, then tap next.
Enter the code received into the text box on the device being activated then tap next.
From the 'Back up?' screen, select one of the following: