If the page you want to have a popup on is not a static one (like blog pages) and you are using the Free version of our plugin, you can insert the popup on the page you wish, inside the index.php file.
Please, follow the steps:
Go to your theme's index.php file and paste the following code:
echo do_shortcode('[sg_popup id="1"]');
NOTE: Don’t forget to backup your current file before modification!
But if you're a PRO user of our plugin, please, follow this article for more details: https://sygnoos.ladesk.com/320734-How-to-set-up-popup-on-pagesposts-PRO-option