Problem extending audio file as custom audio in window 10 video editor

Hi,

I have used video editor in Windows 10 earlier but the second time I am having trouble coordinating the audio file with picture. I am able to add the desired duration to the picture and add custom audio synced to it but the duration of audio file is not adjustable. It appears as if the audio file is not payable in video setting though it is playable individually. I would appreciate if someone can help in managing this issue. Thanks in advance.