If you are using a browser on your mobile device (phone or tablet), EmpCenter will automatically direct you to the Mobile log in page.  Use your ONID username and password to log in, just as you would with the desktop version.  If you need to complete a task in the system that is not available in Mobile, log off and select the Desktop Version link to access the full EmpCenter suite:

empcenter mobile login page with desktop version link at bottom highlighted

Reminder: EmpCenter Mobile is not an App.  You access it using a browser on your mobile device.