Add your gallery posts to Essential Grid
1. Add a couple posts under the "Gallery" tab and make sure all posts have a featured image and a gallery category (no tags).
2. Go to the "Ess. Grid" tab and click on the green settings button of the grid you want to edit.
4. Click on the horizontal "Source" tab
5. Set the "Post Types" setting to "Gallery"
6. Select the categories you want to add (hold ctrl to select multiple)
7. Save the settings in the top right corner
The posts are added to the grid. To show the grid on your website add the "Essential Grid" widget to the page builder. Edit the widget and select the grid you just configured from the dropdown field .