In Semplice 6, you can make images or content fullscreen by adjusting your Section options.
This guide shows you exactly how to do that, using an image module as an example. The image will then be fluid-width, full-height and touch the edges of the browser.
Setting the section as fluid-width
With your content selected (in this case an image), navigate to Section > Options and set Layout to 'Fluid.'
Next, in order to remove the additional gutter spacing around our section we'll need to remove our gutters. Set the Gutter to 'Remove'.
Making the section full-height
You then can also set the height to 'Fullscreen', that will set the minimum height of your section to 100% from your browser viewport. And if you would like your section to be fullscreen on mobile as well, then under the 'Force fullscreen on mobile' option select 'Yes'.