To preview your popups on a mobile device, here's what we recommend.
Open the popup you want to preview in the editor.
In the left menu, click "Display".
Open the page targeting settings.
Target your popup to display on a fictional page of your website such as https://mywebsite.com/wisepops-test or https://mywebsite.com?test. That way, you'll be the only one to have access to this page.
Open this page from any phone.
We recommend you use a testing platform such as BrowserStack to test your popup on different kinds of mobile devices.