Video Borders In Avidemux? Here's Exactly How To Do It

 start avidemux and set audio and video format
Import the video 
Play the video to check it 
On menubar click on video and click on filters 
Click on transform and double click on add borders 
Enter thickness in numbers for each border 
Once done click on ok and then close 
on menubar click on video and click on play filtered option to see applied filters