Write a Code for Integrating Our App as a Popup on Any Website

We have a popup where a Chatbot resides through iframe, we need to integrate this popup in different sites but code should be short so that our clients can easily paste this on their site and popup appears, popup should only take area as the size of popup and when popup is open other contents of website should be clickable. Basically, the popup code should not interfere with website and should be short. Something similar to FreshChat, Zendesk, Verloop, etc