1- Go to your Campaign settings screen of your campaign,
2- In the section « where to show the popups? », uncheck « Show on all pages »
3- in the text input that appears, enter the path of your page like this
PS : if you want to show the popup only on the index/home of a folder like "/blog/", you have to input "/blog/DIR_INDEX", because "/blog/" refers to all pages under that directory.