To integrate with Shopify, you have two options:

First, you can click Get to the right, when you are on the Picreel's webpage in Shopify. With this option, you do not need to install any code. The app is installed via Shopify platform. 

OR, you can install the code manually. In order to do so, please, follow these steps: 

1.Login into your Shopify account.

2.In the menu on the left side click Online Store. Then, Themes. Press Customize theme.



3.Next, you need to navigate to Theme options and click the Edit HTML/CSS option. Please, see the screenshot below.
4.In the Layout folder choose your theme (theme.liquid on the example below). Scroll down to the footer. Then, paste the Picreel code that you get in your account. Click Save.