Fade In

Let's get this flipped MovieClip to fade IN at the same time the original clip is fading OUT:

1. If you haven't done so already, name the new layer Fade In
2. Insert a KeyFrame on the same frame as the Fade Out layer
3. Create Motion Tween

Now fade in from the start of the tween:

1. Select the first keyframe on the Fade In layer
2. Click to select the MovieClip
3. Select Alpha from the Color modifier and change to 0%

The project now looks like this: