Please follow the below video or the following steps to configure Gallery Section on the Homepage of your website.

• Go to Appearance> Customize> Front Page Settings> Gallery Section
• Enter the Button Label
• Click on Add a Widget
• Select Text Widget for title and description of the section
• Enter the Title & Description 
• Again, click on Add a Widget
• Select the Gallery Widget
• Enter the Gallery Title and click on Add Images
• Upload the images and click on Create a New Gallery
• Select the size as Gallery Image from the drop-down

• Click on Insert Gallery
• Click on Publish