To download video, visit the video info page, and then select the drop down menu.
From here select Download Video.
This will provide you with the original source file.
If you uploaded the video as an MP4 you will be provided an MP4.
If you recorded the video using the platform it will be a webm file. However you have the ability to download it as an MP4.
If the video opens in a separate tab, Right click on the video and select Save as....
After you click download MP4, click the MP4 option next to where it says Download:
Here is a tutorial gif.