Add Popup submenu / Add New Popup button
New popups are created on the All Popups admin screen. Open the popup editor by selecting either the Add New Popup button at the top of the screen, or the Add Popup submenu from the plugin admin menu. By default, Popup Maker uses the WordPress classic editor interface for the popup editor.
Enable the WordPress Block Editor in Popup Maker
The block editor introduced in WordPress version 5.0 can be enabled for Popup Maker from the Settings admin page . Go to: ’Settings’ >> ‘General’  and select the checkbox labeled Enable Gutenberg Support .
The block editor is currently available to users as an option. If you encounter a problem while editing a popup, switch back to the classic editor by unchecking the checkbox shown above. Full support for the block editor will be provided in a future version release of Popup Maker.