After installing the app from Shopify, please follow the below guide to integrate the app into your theme.

Select your theme to work on. Open the app and select your theme then click Apply now button to enable embed app. The app will show all themes that you installed in your store, you can select the published or draft theme.

By clicking on the Apply Now button, you will be directed to the Theme editor to enable the app embed. Simply click on the Save button.

Back to the app to continue your work.