The "Full Width Image" element makes it possible to add an image, that is not restricted to the max width of images on the website. The element is found below the tab "Content elements" when creating a new element (img 188.8.131.52).
To choose a picture you need to move on to the 'Image' tab (1). To choose a picture from your filelist click the add image button and select a picture. (img. 184.108.40.206)