Resolution Size. Camera. Build & Run. Please Help.

I have created a game designed for mobile in Unity with AR 9:16. When I am in Unity, I am able to play it and see everything fine. If I try to export it to PC I can only get AR similar to 16:9, which just shows the middle segment of my game. Why can’t I see the whole game as unity shows it - a window of AR 9:16 (tall and thin)?

Please help - driving me crazy!

in my situation, a 16x9 playfield from the project is being cropped in a 16x10 display - how can we adjust the fullscreen in width instead of height?