You can insert gallery widget in WYSIWYG editor or using
Content > Widgets page.
You can choose between two gallery layouts:
Default Magento Gallery:
Masonry Grid Gallery:
Gallery Widget Configuration
Template- select the look of the gallery: default Magento or masonry grid layout
Image Width/Height- set main gallery image size
Thumbnail Width/Height- set thumbnail image size
Images- upload gallery images. You can upload multiple images at once. To assign image alt text, click on uploaded image thumbnail. To change image order, drag image to new position.