Follow the steps to populate your image gallery with pictures.
1. Admin > Customize > Content. Click to edit your app.
2. In the app customization, expand the group, Media under Content. Click on the 'Gallery.'
3. Set up your gallery.
Click on the '+New picture'button, and picture upload options open up. Move on adding any number of images
Move on to the Settingstab. Choose, how many columns the gallery should have per row. One image in each column
4. Click on the 'Create' button to complete creating the gallery.
5. 'Put online' to publish your gallery so that it will appear on your users' devices. The button's caption changes from 'Put online' to 'Published' once the changes have been applied successfully.