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.