To fade the video in, place it in Video Track 2. Leave nothing in Video Track 1. Drag the Cross Fade transition to the Transition Track.

Since you want to leave the screen completely black for 10 seconds, drag the audio and video in Track 2 to start 10 seconds from the beginning of the movie. The Cross Fade should also start at 10 seconds. Adjust the duration of the Cross Fade effect to suit your needs.

Now the movie will start with 10 seconds of blank screen followed by a fade-in of your video content.