If you look at video and audio objects in the program (in timeline mode), you will notice that there are several little, rectangular handles on each object, each of them with different functions. There are handles in the horizontal center at the beginning and end of each object. Those determine the fade-in/fade-out behavior. Just experiment with them to get a feeling for it. (The handles in the lower left-hand and right-hand corner of the object set beginning and end position of the object.) Once again: You need to be in timeline view mode in order to see and control all of this.