The ShowTime theme has had an Instagram widget on the home page since version 3.0. Recently however, Instagram changed their API and the prior method became unreliable.
As of version 3.5 of the theme, I've changed the Instagram functionality to make it more reliable. The Username is no longer needed, but instead an access token (known as the User ID in theme settings) is required.
The good news is, it's easy to obtain the Access Token. First, make sure you're logged into the Instagram account that you want to display on your home page. Then head over to this link:
From there, simply click the "Generate Access Token" button. As long as you're logged into your account, you'll receive a success message that looks like this:
Now, simply paste this long string of numbers and letters into the User ID field in your theme settings area under the Home page - Instagram section. Assuming you've done this properly, your images should appear.
You can now select how many images to show. The images will show in a four-column grid at desktop resolutions, so choosing a value that is a factor of four will yield the best results.