In Semplice 4, you can make images or content full width (or 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 and touch the edge 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' and height to 'Fullscreen'.