How do I give one section a gradient or video background?

Open the section in the builder and go to the Style tab. Then choose a Background Type:

• Colour: pick a Background Colour.
• Gradient: set the colours in Background Gradient.
• Image: choose a Background Image with Browse.
• Video: choose a Background Video with Browse.
• Slideshow: add several images that rotate.

For images and video you also get Background Position and Background Size (Cover or Contain).

Not every section offers every type. Many have only None, Colour, Gradient and Image, while heroes such as Hero Parallax Banner also have Video and Slideshow. Click Save when done.