How to show the popup/conversion mat on a specified page or multiple specified pages?

To show the popups on a specified page :

1-  Go to the edit/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 : /folder/page.html or /long/folder/name/page.php

To show the popups on multiple pages, repeat the same steps until the step 3, then enter the paths of your pages separated by comma « , » like this : "/path/to/page1.html, /page2.html, /folder/page3.html".

Here is a video tutorial about the "Triggers & Targeting"