The Instagram widget in the theme is from Snapwidget. You have to register, but generating a widget is free.
Go to Snapwidget and create an account. Click on "Get a free widget" > "Create a free widget" > select "Instagram Grid" > "Click here to update username" > log in with your account.
Configure the settings like this:
- Thumbnail Size: 250
- Layout (Columns X Rows): 5 x 1
- Photo Padding: 20
- Hover Effect: Fade Out
- Sharing Buttons: No
- Responsive: Yes
Copy the generated code > go to your blog dashboard > Layout > open the "Instagram" widget from the After Footer widget area > paste the code inside.
Set up the widget on mobile like the demo
The demo has two widgets - one for desktop (5x1) and one for mobile (2x2), since using the 5x1 widget everywhere means the images on mobile will be very small.
To add a mobile widget, too, generate another Instagram widget and configure all the settings the same way, except for Layout (Columns X Rows) - it should be 2 x 2 instead of 5 x 1.
Copy the generated code > go to your blog dashboard > Layout > open the "Instagram" widget from the After Footer widget area > use the HTML below and insert the widgets between the classes:
<div class="instagram-outer">
<h3 class="title">my title</h3>
<div class="instagram-inner">
<div class="instagram-desktop">
<!-- add the desktop Instagram widget here -->
</div>
<div class="instagram-mobile">
<!-- add the mobile Instagram widget here -->
</div>
</div>
</div>