Firstly, please make sure that you created at least one subscription rule and selected product(s) to apply the rule.
Remember to check the result on the product page that you selected to apply the rule.
Secondly, please integrate the app with the theme you want to show the widget. (You want to integrate the app to a copy of your live theme to test first. Therefore, you should preview this copied theme to check the subscription widget).
If you still cannot figure it out, don’t hesitate to contact us via email or live chat.