One way to use masks in Adobe Premiere is by making it a transition mask. Transitions allow you to smoothly move between one clip and the next. The transition mask uses a black and white image of your choice as the transition image. As your clips transition from one to another, the first clip takes the place of the black in the transition image, and the next clip takes the place of the white. This makes for an interesting and fun transition.
To use this mask, follow the below procedures:
1. Go to Tasks, and then Edit.
2. Select Transitions from the Edit panel.
3. In the Transition menu, click on Video Transitions and Special Effects.
4. In this menu, scroll down to Image Mask transition.
5. Select and drag the Image Mask transition option to the Timeline and place it between the two clips where you want the transition.
6. Go to the Image Mask Settings dialog box, and click on Select Image
7. Find the image that you want to use as your transition image, and select Open.
8. Hit OK.