This may or may not be your first trophy in the game, it depends on whether you chose to calibrate or not when the game asks you after creating your save data.
Simply complete the audio and video feedback tasks or enter in your own calibration numbers which you could have used in other Rock Band games.
You could also use the automatic calibration method if you have a Rock Band 2 guitar, the Rock Band 1 guitar won't work for this method.
The trophy comes up when you have completed Calibration.