There are various methods but telling your simple and easy one.
1. Put cursor on the object (piece of music individual or select all on the track) then press down. Do it little by little and listen when you are satisfied stop.
2.THE EASIEST WAY: click "M" on the key board to open Mixer, use the slider to reduce the volume of track. Or under arranger right below click on the Mixer button (like four lines to turn on and off).
Other hints
3. For Normalization of entire project click Alt+M
4. Put cursor on the desire object Right click from drop down menu select Volume then do as you please.