Help with Cubase AI4 Please!

I recently bought a Yamaha KX8 that came with a copy of Cubase AI4 and had some troubles setting it all up but got there in the end. But whenever I set the keyboard up on Cubase and add any VST track I can’t get any sound at all! Everything seems to be working fine up until I start touching the keys and no sound is produced.

Does anyone know what the problem might be?

Also I’m very new to all this, so the more idiot-proof the instructions, the better! :laughing: