EcomSend is committed to providing customers with an out-of-box user experience, there are only two steps to display the popup on your storefront.

Here is the instruction

Step 1 - Enable the app embed
Go to EcomSend admin → Dashboard tab → click Enable app embed button or Enable the app embed button to activate the app embed → save your changes in the Shopify theme editor

Note: if you have changed your store theme, you need to re-enable the app embed.

App embed is a new way highly recommended by the Shopify official team to install the app's necessary scripts. It is clean and safe, has one-click activation and one-click deactivation, no code residue after app uninstallation, and abandons the way that other apps need to change merchants' store theme code.
Here is an introduction document by Shopify: https://shopify.dev/apps/online-store/theme-app-extensions/extensions-framework

Step 2 - Customize and Publish your popup
Go to EcomSend admin → Popups tab → customize the popup to match your brand → toggle the widget on by clicking the blue switch

Need help? Feel free to contact us via online chat or email, our world-class 24/7 support team is always glad to help you ?