Hello,
Please watch these videos – https://youtu.be/OnxkixHtVLI https://youtu.be/f07MBdnFPfk
You can use settings of menu item to set width and height of mega menu + static blocks can be used there – http://prntscr.com/py1lzf (this is screenshot from default demo – https://xstore.8theme.com/)
Regards