The gallery widget is simply an element to display images either within a grid or an interactive carousel.
Adding images
To add an image or multiple images, select the edit images tab
Edit the styling
There are two main styling options to chose from: Grid and Carousel. A grid layout will display a static format of all the images you add. Carousel enables you to add movement to your images or manual user input to scroll though such images.
Both have the same styling elements from image ration 'size' Open images in lightbox 'enlarges image when clicked and if you want the image to fill the container size.
If your choice was to select the carousel option you have the ability to display navigation arrow to display so the visitor can scroll though the images manually or change the slides automatically based on time.