On the Windows 8 Start screen, click on user name (the current logged user). Windows 8 will list out other users from the drop out panel. In this example, I am currently logged as Local account. So, to switch over Microsoft account, click on the user (ITsiti dotCom).
Windows 8 will ask you to key in the password and press Enter once finished.
You are now logged in as Microsoft account. To switch to Local account, do as the same steps above.