The Sections Slider is a custom Visual Composer element in UX Shop, which you can use to easily create a slider using the content of multiple sections you have previously created. Just add the Sections Slider element, and add some Sections to it. Clicking the pencil icon on the Section Slider element, you can set some basic settings such as the slider effect, autoplay etc.
The dimensions of the sections slider are determined by the container it is in, and by the contents of it. If you want to set the width of the Section slider to be equal to the full window width, since it is contained in a Visual Composer row, you must go into that's row settings and set it to 'Stretch row and content (no paddings)'
On the other hand if you want to set the height of the section slider, lets say to 100% the window height, you must set the height of each one of the slides. The Sections Slider will automatically adust it's height to match the visible slide's height.
So to set the Section Slider to match the window's height, you must set each slide to match the window's height. You must do that by setting the Full height row to 'Yes' in the Row settings of the row that contains the section's content. In this case you should have only one (outer) row.
Also on the meta box 'General Section Settings' you should set Height / Padding to No padding, and check Full Width