Ok, there’s two things you can try.
But before you try this, make sure you’re not trying to get a 16:9 (widescreen) frame into a standard 4.3 frame. I would imagine you already checked that.
1. Select the clip(s) in the timeline and right click, from the pop up menu click on the “Scale to frame size” option. That should scale it right to the correct frame size.
2. Select the clip in the footage que (Not the timeline), then go to file, and scroll down to the “interpret footage”. When the screen comes up select the proper settings.
Again though, this wont look right unless your footage and project ratios are the same, 16.9(wide) with 16.9(Wide) or 4.3(Standard) with 4.3(standard).
Good luck.