How-to: Fade in or out
To Fade a channel, go to Automate and in the drop down menu click on Volume.
An automation line will appear.
Click anywhere in the track and an automation point will appear. This is two channels "cross fading":
You can do this with any of the individual channels, but if you want to fade in or out an entire song then you have to use the Master Channel automation settings.
Start by clicking View -> Show Master Channel. The master channel will appear in the bottom of your arrange. Now you can use the volume automation on the master channel to fade in your song.