Your descriptions "synth track" and "instrument track" leave room for interpretation. I guess you mean MIDI track and audio output track (unless they've changed the naming). A "simple instrument track" means a combination, where the audio track is hidden, sort of. It's better to start with separate MIDI and audio tracks, though, in order to learn about the "roots".
The MIDI notes must, obviously, be pasted or dragged into the MIDI track.
If that's where the mistake took place, you're up and playing in no time.