How to Create a Shortcode for Instagram Slider Widget
1. First of all, please ensure that you've installed and activated the Instagram Slider Widget plugin.
2. Navigate to "Appearance > Widgets" and drag "Instagram Slider" to the "Instagram Slider - Shortcode Generator" area.
3. After you're done with your settings, click Save and you'll see the shortcode over there:
4. Once you get your shortcode, just go to "Appearance > Customize > 7. Footer > 7.2. Instagram Slider Widget" and place it into the shortcode field. That's all.
By the way, the widget settings on our demo site is like below: