Hi
If your image is poitrait format then VP will not distort (stretch) it to fit the standard 16:9 landscape format. It will fit it into the frame height leaving black bars on each side.
To remove these and make the image fit the frame you can use CROP but forcing the 16:9 format. In version 3.47 click the 16:9 option and then use the X1 or Y1 sliders to reduce the rectangle seen in the preview. You can drag this rectangle around also with the mouse until it frames the part of the image that you wish to retain.It will then be full frame 16:9
Unless you distort the image (using SCALE) you will always lose some part of it at top and bottom.
The VP frame will always be 16:9 so any portrait image will have the black sidebars.
Nat