The Background Tool can be opened by clicking on the following icon.
The Background Tool has 3 main options.
Apply a flat colour as the canvas background.
Apply a grid as the canvas background. This can be helpful to align or to measure them moving or resizing elements. The grid option comes with two sizes. 25mm/1" or 50mm/2".
Apply an image as the canvas background. The tool will show you any images that are in the special category called Backgrounds in the Images library.