It’s really easy to limit the display of a popup to new visitors only
1.
 Log in to your account
2. Create a popup or edit one that already exists
3. Go on the “Display rules” tab
4. Look for the sentence “Never display again after — visits” and type “1” as the value.
5. Save

Now your popup will never be displayed again to people that already came on your website before (based on the cookie-duration).