To replace videos with an existing URL:
Log-in to Hippo Video with your existing credentials.
Click on the Library icon from the left navbar.
Now, click on All Videos and then select the existing video you want to replace.
In the video preview page, hover your mouse over the video.
Click the Camera icon to the upper right side of the video.
Select the video from your local drive. It will take a few minutes to replace the video.
Once done, you’ll be redirected to the Video Preview page.
You will notice that the selected video is replaced with the existing one.
Note: The existing video will be pushed to the Library (video title name will have the text OLD added as a suffix to it).
Here's a quick video on how to replace a video,