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): 4 x 1
- Photo Padding: 30
- Hover Effect: None
- 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.
<div class="instagram-outer">
<h3 class="title">instagram</h3>
<div class="instagram-inner">
<!-- remove this line and add the Instagram widget here -->
</div>
</div>