Add Photo Gallery
You can create new gallery pages and configure them to look like the demo by enabling Jetpack image features. Once you have activated and connected the Jetpack Plugin, go to Jetpack → Settings → Performance and activate Speed up image load times to enable this feature.
Then create a new page, add the gallery in by clicking Add Media. Then click Create New Gallery and select the pictures you want. The last screenshot below shows the settings for the tiled gallery.