Photo galleries are inserted and managed in the same place as individual images. Click on the “Add image” button next to Add Media, then upload a file or add the link to one that already exists. You’ll see a link across the top that says “Gallery” and has a number in parentheses. This number tells you how many images are in the gallery. Click the Gallery link to view the images and reorder them or edit them, including the captions and full descriptions.
To insert the gallery on the page, make sure you have at least 2 images total, click on the “Gallery” link across the top of the image editing window, then scroll to the bottom and click the “Insert gallery” button.