I am new to Final Cut Pro X and also very confused lol. When I exported my video, I just realized later on that it has big black bars around the frame! It's really annoying to see those black bars taking space, any suggestion on how to get rid of them?
Link to the vid:
Looks like your footage didn't match your project aspect ratio.
It looks like this is a timeless made from stills. Your camera probably shoot stills at a 3:2 (like 5760x3840) aspect ratio, but you video is 16:9 (3840x2160).
You'll need to scale and crop your stills to match your project setting, or set your project to match your stills. Generally people like to use 16:9 for video so scaling and cropping your photos is the way to go.