I can not setup microphone in Cubase. Le 8.
I am using the Alesis Multmix4 mixer.
Have you assigned the ASIO driver for your Alesis Multmix4 mixer in the Cubase>Devices>Device Setup>VST Audio System menu?
Once you do that, then the Alesis inputs and output buses should be listed in the Cubase>Devices>VST Connections menu.
Regards