Is there a way to trigger the popup on clicking a button?
1. In the popup editor, step 3 Display Rules -> Display Rules tab, make sure the popup is enabled on the page or post that you are going to add the button.
2. If you don't like the popup to show up automatically, in the popup editor, step 3 Display Rules -> Display Time, uncheck all options.
3. In the page or post that you are going to add the button, switch to Text edit mode, add the following code to create a button that will tigger the popup on click.
Please make sure to change value of data-popupid to the ID of your own popup.
<a href="#" class="wppopup" data-popupid=2><button>Show Popup</button></a>
A demo is as follows: