Installing a popup on your WordPress is easier than you think. But before installation, you of course need to create a popup.
You can do this by using Serviceform's free, no-code popup builder. Once you've done that, go to your WordPress account and find the 'Serviceform Pixel' WordPress plugin.

After you've found it, search for your pixel ID from your Serviceform account. Then enter the pixel ID into the Serviceform plugin you’ve already installed.
Another way to do it is to add the Serviceform pixel code directly into the head tag of your website. Simply copy and paste your Serviceform pixel code into the head tag and your popup's ready to go.