To preview your popups on a mobile device, here's what we recommend.
Step 1:
Open the popup you want to preview in the editor.
Step 2:
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.
Step 3:
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.