On mine I do this.
I connect the phone and turn it on.
It asks me what I want to do with the usb connection and I select "File Transfer".
(yours might vary)
I can then see the phone on my computer.
I then click on Internal shared storage.
Then I click on DCIM
I then click on Camera
I can then see the video file(s) and can then drag them to an appropriate folder on my computer.
I then go to youtube and can send the file from my computer.
I imagine you can do it direct from the phone but have never done that. I always edit my stuff first so it has to be on the computer first.
Hope this helps. Your folder names and locations may be different.
Mart.