Hello,

What version of Cubase are you on? What operating system?

Perhaps it would be best to start back from the start.

File, New Project, Empty.

Import a stereo audio file into the project.

Go to Project, Add Track, FX Channel, and load a reverb plugin. Set the reverb plugin to 100% send.

On the audio track, hit the inspector button (looks like a lower case "e"). This will open the VST Channel settings. On the right, you have sends. Click in the first slot and select FX 1. Click on the circle with the line at the top to activate the send, and then drag the bar below it to the right to determine the send amount.

I hope this helps.