I'm only here because I wanted to recommend this programme to a friend. I have used it for years, pushing it to the limit and it is utterly brilliant. I now do some work for a community radio station and use this for my audio editing [!] I find it quicker than Audacity, which all my colleagues use.
Guest, Drag the little blue arrow head in the audio track back towards the beginning of the track. Visa versa for fade in. Or click on the track and in the properties tab on the right side, click Volume, show keyframes, add a keyframe where you want the fade to start and then add a keyframe where you want it to stop and then drag the stop red keyframe marker down to the level you want at the end.