Open the Facebook app on your phone
Find the video you want to download
Tap the three dots on the post
Check if a Download video option is available
If available, tap Download video
If not available, open the video in your browser
Copy the video link
Use a trusted Facebook video downloader website
Paste the link into the downloader
Select the video quality if prompted
Tap Download
Save the file to your phone
Open your phone’s Files or Gallery app to find the video
Make sure you have permission to download and use the video