OK, load into the timeline the clips you want to show (place them on different tracks) at the end of each clip you will find a box like icon called pan and crop (don't mean to offend if you already know this but it's better than questions floating back and forward). Click on the first track pan and crop icon, a new work space will apear with the video in there. Around the picture you will notice a dashed line and boxes, click on one of the boxes on the corner of the picture and drag it outwards. you will now see your picture in the video preview shrinks, get it to the size you want and then place it anywhere on the screen you feel looks right. Now at the bottom of the workspace you will see the area for key frames 'position and mask', check the mask box, On the left hand side now you will notice another new area, click on the top 'fountain pen' icon, now place 4 markers on your video in each corner but in from the edge and create a 'border' around you picture, make sure that in 'path / mode' is set to positive, click feather type 'in/out/both' then feather %. job done, get back to me if this is not clear.