No need to resize them. The problem isn't the size, it's the shape. The pictures are taller & narrower than the video frame. If you look carefully you'll see that the entire picture is shown, but it isn't wide enough to fill the frame. Open up Pan/Crop, right-mouse-button click on the frame, and select "Match Output Aspect". This will cut off enough of the top & bottom of the photograph so that it will now fit side to side.

Note that when the shape doesn't match exactly, something has to give. Either you'll have empty space on two edges, or you'll lose some of two edges of the picture, or a bit of both, or you have to stretch the image some to make it fit (which you've already tried). There's no way around this, it's just simple geometry.

Like I said, Kelly ;-)

Great thanks, that did the trick!

Another lesson learned.

Also if you incorporate a matching / enhancing (white, black, etc.) backgound, you get to see the whole picture without it looking too bad.

Something else you can do. Not that I would recommend it for every day use. If you're trying to fill a frame with a still image, work it in Photoshop (or something else) first.

Not only can you crop and resize you can use the cloning tools to expand the background* and if you do a good job, nobody will be the wiser. Things like the rubber stamp, healing brush, etc., work for the times you can't really crop and just jump it up to meet the frame aspect ratio of your project.

* with a little effort you can enlarge/shrink your subjects in the foreground, using layers, and/or jimmy up the background then put it all together in perfect 4/3 ratio or whatever you need. Very straightforward to add or take away some trees, buildings, etc..