Up to SharePoint 2010 you could log into the site as a different user by going to the Welcome menu and selecting ‘Sign in as different user’.
Come SharePoint 2013 you go to do the same and yikes! there’s just an option to sign out! What do you do when you want to sign in with a different account?
Actually it’s quite easy. Just go to:
<SITE URL>/_layouts/15/closeConnection.aspx?loginasanotheruser=’true’
You’ll be prompted to sign in and can enter the user credentials.