In «Style», «Background» sets the type of background: a solid colour, a gradient, a pattern or an image.
On a solid colour you can add a light texture. On a pattern or an image you can lay a colour veil, so the text on top stays readable.
The preview on the right changes as you type. When you are done press «Save»: until you save, visitors see the previous version.
Still stuck?
Terms and definitions live in the glossary; for anything else there’s support.