You have several options here, and you didn’t really indicate fully what you want to do.
Also unknown is the resolution you’re working with.
Source resolution: 1080x1920
Language: English (Translated filter names may be different)
Option #1
Filling the width.
Step 1. Set Video Mode to a 1080p preset.
Step 2. Open video or image.
Step 3. Apply filter Crop:Source to the video or image.
Check “Center” and use Center Bias to position where you want to position the video or image.
Option #2
Blurring the blank space to the left/right.
Step 1. Set Video Mode to a 1080p preset.
Step 2. Open video or image.
Step 3. Apply filter Blur: Pad to the video or image.
Option #3
Rotating the video.
Step 1. Set Video Mode to a 1080p preset.
Step 2. Open video or image.
Step 3. Apply filter Size, Position & Rotate to video or image.
Apply a rotation of either 90 degrees or 270 degrees.
Change size to 1080x1920.
