You didn’t list system or hardware specs so I am assuming you mean a midi keyboard connected to a PC (Windows) computer through a USB connection…
If no… Then these instructions might not apply.
-Connect and make sure your PC recognizes the USB keyboard before starting Cubase.
-Start Cubase. It will automatically detect the keyboard.
-Turn on the keyboard and make sure it is set to send midi. You might have to press a button or a series of keys on your keyboard to set this. This procedure would be in your keyboard op manual.
-Add an instrument track, choose “All midi inputs” and choose ezdrummer2 as the vst instrument.
You should be all set.